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Zwitterionic thiolate ligands have the potential to introduce novel assembly modes and functions for noble metal clusters. However, their utilization in the synthesis of silver clusters remains understudied, particularly for the clusters containing reductive Ag(0) species. In this article, we report the first synthesis of a mixed-valence silver(0/I) cluster protected by zwitterionic Tab as thiolate ligands (Tab = 4-(trimethylammonio)benzenethiolate), denoted as [Ag 22 (Tab) 24 ](PF 6 ) 20 ·16CH 3 OH·6Et 2 O ( Ag 22 ·16CH 3 OH·6Et 2 O), alongside an Ag(I) cluster [Ag 20 (Tab) 12 (PhCOO) 10 (MeCN) 2 (H 2 O)](PF 6 ) 10 ·11MeCN ( Ag 20 ·11MeCN). Ag 22 has a distinct hierarchical supratetrahedral structure with a central {Ag 6 } kernel surrounded by four [Ag 4 (Tab) 6 ] 4+ units. High-resolution electrospray ionization mass spectra demonstrate that Ag 22 has two free electrons, indicating a superatomic core. Ag 20 has a drum-like [Ag 12 (Tab) 6 (PhCOO) 6 (H 2 O)] 6+ inner core capped by two tetrahedral-like [Ag 4 (Tab) 3 (PhCOO) 2 (MeCN)] 2+ units. Ag 20 can be transformed into Ag 22 after its reaction with NaBH 4 in solution. Antibacterial measurements reveal that Ag 22 has a significantly lower minimum inhibitory concentration than that of the Ag 20 cluster. This work not only extends the stabilization of silver(0/I) clusters to neutral thiol ligands but also offers new materials for the development of novel antibacterial materials.

We report the synthesis and structural characterization of a 2D metal-organic framework with AB-packing layers, [Co 2 (pybz) 2 (CH 3 COO) 2 ]·DMF ( Co2 , pybz= 4-(4-pyridyl)benzoate), containing a stable (4,4)-grid network fabricated by paddle-wheel nodes, ditopic pybz, and acetate ligands. After removal of the guest, the layer structure is retained but reorganized into an ABCD packing mode in the activated phase ( Co2a ). Consequently, the intralayer square windows (7.2 × 5.0 Å 2 ) close, while the interlayer separation is decreased slightly from 3.69 to 3.45 Å, leaving a narrow gap. Importantly, the dangling methyl group of the acetate with H-bonds to the adjacent layers and also the well-distributed π-π interactions between the aromatic rings of neighboring layers facilitate the structural stability. These weak supramolecular interactions further allow for favorable dynamic exfoliation of the layers, which promotes efficient adsorption of C 2 H 2 (41.6 cm 3 g -1 ) over CO 2 with an adsorption ratio of 6.3 (0.5 bar, 298 K). The effective separation performance of equimolar C 2 H 2 /CO 2 was verified by cycling breakthrough experiments and was even tolerable to moisture (R.H = 52%). DFT calculations, in situ PXRD, and PDF characterization reveal that the favorable retention of C 2 H 2 rather than that of CO 2 is due to its H-bond formation with the paddle-wheel oxygen atoms that triggers the increase in interlayer separation during C 2 H 2 adsorption.

Three new ligands based on the alloxazine core appended with pyridyl coordinating groups have been designed, synthesized, and characterized. The ligands are revealed to be redox-active in DMF solution, as attested to by CV and combined CV/EPR studies. The spin of the reduced species appears to be delocalized on the alloxazine core, as attested to by DFT calculations. The coordination abilities of one of the ligands toward Cu 2+ or Ni 2+ 3d cations revealed the formation of the first alloxazine-based 3D coordination polymers, presenting strong π-π stacking and substantial cavities. Preliminarily charge/discharge experiments in Li batteries evidence Li + insertion in such systems.

The mechanism of isomerization of the known 2-phenyl,pyridine ( phpy ) derivatives [Ru( phpy -κC,N) (MeCN -trans- N)( terpy )]PF 6 , 2 , to [Ru( phpy -κC,N)(MeCN -trans- C)( terpy )]PF 6 ( terpy = 2,2';6',2″-terpyridine), 3 , at temperatures >50 °C has been investigated both by 1 H NMR spectroscopy and by DFT calculations. The photoisomerization of 2 to 3 by UV light occurred also quantitatively in MeCN after 20 h at room temperature. A similar behavior to that of 2 could be established for the related compound [Ru(3-acridine-2'-C 5 H 4 N-κC,N)(MeCN -trans- N)(2,2';6',2″-terpyridine)]PF 6 , 6 (acridine = dibenzo[ b , e ]pyridine or 2,3-benzoquinoline), that was obtained from the reaction between [Ru(3-acridine-2'-C 5 H 4 N-κC,N) (MeCN) 4 ]PF 6 , 4 , and terpy in MeOH/MeCN at 60 °C for 24 h. Similar to 2 , the isomerization of 6 to [Ru(3-acridine-2'-C 5 H 4 N-κC,N)(MeCN -trans- C) ( terpy )]PF 6 , 7 , could be induced thermally (48 h at 60 °C in pure MeOH) or photochemically under UV radiation in MeCN at room temperature. A compound closely related to 7 but in which MeCN was replaced by H 2 O was described earlier (Tanaka et al. Inorg. Chem. 2012 , 51, 5386-539). The presence of water on this compound had a dramatic effect as far as the coordination of terpy was concerned as its isomerization to a compound related to 6 (in which H 2 O instead of MeCN is coordinated to Ru) occurred indeed photochemically via irradiation with visible light.

The structure, bonding, and properties of a series of atypical pentanuclear nickel hydride clusters supported by electron-rich i Pr 3 P of the type [( i Pr 3 P)Ni] 5 H n ( n = 4, 6, 8; H 4 , H 6 , H 8 ) and their anionic models where i Pr 3 P are substituted by H - ( H 4 ' , H 6 ' , H 8 ' ) were investigated by density functional theory (DFT) calculations. All clusters were calculated to adopt a similar square pyramidal core geometry. Calculations indicate singlet ground states with small singlet-triplet gaps for H 4 and H 6 , similar to previously reported experimental values. Molecular orbital theory description clusters were investigated using the simplified model complexes [HNi] 5 H n 5- ( n = 4, 6, 8; H 4 ' , H 6 ' , H 8 ' ). The results show that there are three skeletal electron pairs (SEPs) in H 4 ' . The addition of two molecules of H 2 to form H 6 ' and H 8 ' results in the partial or full occupation of two degenerate MOs ( e* set) that give two SEPs and one SEP, respectively. Indeed, the occupation of these low-lying weakly antibonding orbitals governs the multielectron chemistry available for these clusters and plays a role in their unique reactivity.

A rare example of pyrimidine-based ESIPT-capable compounds, 2-(2-hydroxyphenyl)-4-(1 H -pyrazol-1-yl)-6-methylpyrimidine ( HL H ), was synthesized (ESIPT─excited state intramolecular proton transfer). Its reactions with zinc(II) salts under basic or acidic conditions afforded a dinuclear [Zn 2 L H 2 Cl 2 ] complex and an ionic (H 2 L H ) 4 [ZnCl 4 ] 2 ·3H 2 O solid. Another ionic solid, (H 2 L H )Br , was obtained from the solution of HL H acidified with HBr. In both ionic solids, the H + ion protonates the same pyrimidinic N atom that accepts the O-H···N intramolecular hydrogen bond in the structure of free HL H , which breaks this hydrogen bond and switches off ESIPT in these compounds. This series of compounds which includes neutral HL H molecules and ionic ( L H ) - and ( H 2 L H ) + species allowed us to elucidate the impact of protonation and coordination coupled deprotonation of HL H on the photoluminescence response and on altering the emission mechanism. The neutral HL H compound exhibits yellow emission as a result of the coexistence of two radiative decay channels: (i) T 1 → S 0 phosphorescence of the enol form and (ii) anti-Kasha S 2 → S 0 fluorescence of the keto form, which if feasible due to the large S 2 -S 1 energy gap. However, owing to the efficient nonradiative decay through an energetically favorable conical intersection, the photoluminescence quantum yield of HL H is low. Protonation or deprotonation of the HL H ligand results in the significant blue-shift of the emission bands by more than 100 nm and boosts the quantum efficiency up to ca. 20% in the case of [Zn 2 L H 2 Cl 2 ] and (H 2 L H ) 4 [ZnCl 4 ] 2 ·3H 2 O . Despite both (H 2 L H ) 4 [ZnCl 4 ] 2 ·3H 2 O and (H 2 L H )Br have the same ( H 2 L H ) + cation in the structures, their emission properties differ significantly, whereas (H 2 L H )Br shows dual emission associated with two radiative decay channels: (i) S 1 → S 0 fluorescence and (ii) T 1 → S 0 phosphorescence, (H 2 L H ) 4 [ZnCl 4 ] 2 ·3H 2 O exhibits only fluorescence. This difference in the emission properties can be associated with the external heavy atom effect in (H 2 L H )Br , which leads to faster intersystem crossing in this compound. Finally, a huge increase in the intensity of the phosphorescence of (H 2 L H )Br on cooling leads to pronounced luminescence thermochromism (violet emission at 300 K, sky-blue emission at 77 K).

Cu chelation in biological systems is of interest as a tool to study the metabolism of this essential metal or for applications in the case of diseases with a systemic or local Cu overload, such as Wilson's or Alzheimer's disease. The choice of the chelating agent must meet several criteria. Among others, affinities and kinetics of metal binding and related metal selectivity are important parameters of the chelators to consider. Here, we report on the synthesis and characterization of Cu-binding properties of two ligands, L1 and L2, derivatives of the well-known peptidic Cu II -binding motif Xxx-Zzz-His (also called ATCUN), where Cu II is bound to the N-terminal amine, two amidates, and the imidazole. In either L, the N-terminal amine was replaced with a pyridine, and for L2, one amide was replaced with an amine compared to Xxx-Zzz-His. In particular, L2 showed several interesting features, including a Cu II -binding affinity with a log  K D app = -16.0 similar to that of EDTA and stronger than all reported ATCUN peptides. L2 showed high selectivity for Cu II over Zn II and other essential metal ions, even under the challenging conditions of the presence of human serum albumin. Further, L2 showed fast and efficient Cu II redox silencing qualities and Cu II -L2 was stable in the presence of mM GSH concentrations. Benefitting the fact that L2 can be easily elongated on its peptide part by standard SPPS to add other functions, L2 has attractive properties as a Cu II chelator for application in biological systems.

Quantum entanglement between the spin states of a metal center and radical ligands is suggested in an iron(II) [Fe(dipyvd) 2 ] 2+ compound (dipyvd = 1-isopropyl-3,5-dipyridil-6-oxoverdazyl). Wave function ab initio (Difference Dedicated Configuration Interaction, DDCI) inspections were carried out to stress the versatility of local spin states. We named this phenomenon excited state spinmerism , in reference to our previous work (see Roseiro et al., ChemPhysChem 2022 , e202200478) where we introduced the concept of spinmerism as an extension of mesomerism to spin degrees of freedom. The construction of localized molecular orbitals allows for a reading of the wave functions and projections onto the local spin states. The low-energy spectrum is well-depicted by a Heisenberg picture. A 60 cm -1 ferromagnetic interaction is calculated between the radical ligands with the S total = 0 and 1 states largely dominated by a local low-spin S Fe = 0. In contrast, the higher-lying S total = 2 states are superpositions of the local S Fe = 1 (17%, 62%) and S Fe = 2 (72%, 21%) spin states. Such mixing extends the traditional picture of a high-field d 6 Tanabe-Sugano diagram. Even in the absence of spin-orbit coupling, the avoided crossing between different local spin states is triggered by the field generated by radical ligands. This puzzling scenario emerges from versatile local spin states in compounds which extend the traditional views in molecular magnetism.

A series of ten cationic complexes of the general formula [(C^C)Au(P^P)]X, where C^C = 4,4'-di- tert -butyl-1,1'-biphenyl, P^P is a diphosphine ligand, and X is a noncoordinating counteranion, have been synthesized and fully characterized by means of chemical and X-ray structural methods. All the complexes display a remarkable switch-on of the emission properties when going from a fluid solution to a solid state. In the latter, long-lived emission with lifetime τ = 1.8-83.0 μs and maximum in the green-yellow region is achieved with moderate to high photoluminescence quantum yield (PLQY). This emission is ascribed to an excited state with a mainly triplet ligand-centered ( 3 LC) nature. This effect strongly indicates that rigidification of the environment helps to suppress nonradiative decay, which is mainly attributed to the large molecular distortion in the excited state, as supported by density functional theory (DFT) and time-dependent DFT (TD-DFT) computation. In addition, quenching intermolecular interactions of the emitter are avoided thanks to the steric hindrance of the substituents. Emissive properties are therefore restored efficiently. The influence of both diphosphine and anion has been investigated and rationalized as well. Using two complexes as examples and owing to their enhanced optical properties in the solid state, the first proof-of-concept of the use of gold(III) complexes as electroactive materials for the fabrication of light-emitting electrochemical cell (LEC) devices is herein demonstrated. The LECs achieve peak external quantum efficiency, current efficiency, and power efficiency up to ca. 1%, 2.6 cd A -1 , and 1.1 lm W -1 for complex 1PF 6 and 0.9%, 2.5 cd A -1 , and 0.7 lm W -1 for complex 3 , showing the potential use of these novel emitters as electroactive compounds in LEC devices.

α-Pyridyl thiosemicarbazones (TSC) such as Triapine (3AP) and Dp44mT are a promising class of anticancer agents. Contrary to Triapine, Dp44mT showed a pronounced synergism with Cu II , which may be due to the generation of reactive oxygen species (ROS) by Dp44mT-bound Cu II ions. However, in the intracellular environment, Cu II complexes have to cope with glutathione (GSH), a relevant Cu II reductant and Cu I -chelator. Here, aiming at rationalizing the different biological activity of Triapine and Dp44mT, we first evaluated the ROS production by their Cu II -complexes in the presence of GSH, showing that Cu II -Dp44mT is a better catalyst than Cu II -3AP. Furthermore, we performed density functional theory (DFT) calculations, which suggest that a different hard/soft character of the complexes could account for their different reactivity with GSH.

Biphenol-based ligands have proven their ability to bind titanium(IV) centers and generate sophisticated self-assembled structures in which auxiliary nitrogen ligands often complete the coordination sphere of the metal and improve stability. Here, a central 4,4'-bipyridine, which acts as both a spacer and a source of monodentate nitrogen to complete the coordination sphere of the Ti(IV) complex, was incorporated within two bis-2,2'-biphenol strands, 3 H 4 and 4 H 4 . Both proligands possess structural features that are well adapted to form self-assembled structures built from titanium-oxygen-nitrogen units; however, their different degrees of torsional freedom strongly influenced the nuclearity of the complexes formed. The presence of a phenyl spacer between the bipyridine and the biphenol moieties of 3 H 4 provided enough flexibility for the ligand to wrap around one titanium(IV) center to form a mononuclear complex Ti( 3 )(DMF) 2 in the presence of dimethylformamide (DMF). Assembly of the more rigid ligand 4 H 4 with Ti(O i Pr) 4 afforded a tetranuclear complex Ti 4 ( 4 ) 2 ( 4 H) 2 (OEt) 2 containing four stacked 4,4'-bipyridine units as shown by the X-ray structure of the complex. Density functional theory studies suggested that the assembly of this tetrametallic complex involves a dimetallic intermediate with TiO 6 nodes that is converted to the thermodynamically stable tetranuclear complex with two TiO 6 nodes and two TiO 5 N units with enhanced covalent character.

The steric strain around copper(I) in typical [Cu(NN R ) 2 ] + complexes, where NN R is a diimine ligand substituted in α-positions of the nitrogen atoms by R, is known to strongly impact the excited-state properties. Generally speaking, the larger the R, the longer the emission lifetime and the higher the quantum yield. However, the stability of the coordination scaffold can be at stake if the steric strain imposed by R is too large. In this work, we explore a way of fine-tuning the steric strain around Cu(I) to reach a balance between high emission quantum yield and stability in a highly bulky copper(I) complex. Taking stable [Cu(dipp) 2 ] + and unstable [Cu(dtbp) 2 ] + (where dipp and dtbp are, respectively, 2,9-diisopropyl-1,10-phenanthroline and 2,9-di- tert -butyl-1,10-phenanthroline) as the boundary of two least and most sterically strained structures, we designed and characterized the nonsymmetrical ligand 2-isopropyl-9- tert -butyl-1,10-phenanthroline (L1) and corresponding complex [Cu(L1) 2 ] + (Cu1). The key experimental findings are that Cu1 exhibits a rigid tetrahedral geometry in the ground state, close to that of [Cu(dtbp) 2 ] + and with an intermediate stability between that of [Cu(dipp) 2 ] + and [Cu(dtbp) 2 ] + . Conversely, the nonsymmetrical nature of ligand L1 leads to a shorter emission lifetime and smaller quantum yield than those of either [Cu(dipp) 2 ] + or [Cu(dtbp) 2 ] + . This peculiar behavior is rationalized through the in depth analysis of the ultrafast dynamics of the excited state measured with optical transient absorption spectroscopy and theoretical calculations performed on the ground and excited state of Cu1. Our main findings are that the obtained complex is significantly more stable than [Cu(dtbp) 2 ] + despite the sterically strained coordination sphere. The nonsymmetrical nature of the ligand translates into a strongly distorted structure in the excited state. The distortion can be described as a rocking motion of one ligand, entailing the premature extinction of the excited state via several deactivation channels.

Iron carboxylates are widely used as iron precursors in the thermal decomposition process or considered as in situ formed intermediate precursors. Their molecular and three-dimensional (3D)-structural nature has been shown to affect the shape, size, and composition of the resulting iron oxide nanoparticles (NPs). Among carboxylate precursors, stearates are particularly attractive because of their higher stability to aging and hydration and they are used as additives in many applications. Despite the huge interest of iron stearates, very few studies aimed up to now at deciphering their full metal-ligand structures and the mechanisms allowing us to achieve in a controlled manner the bottom-up NP formation. In this work, we have thus investigated the molecular structure and composition of two iron stearate precursors, synthesized by introducing either two (FeSt 2 ) or three (FeSt 3 ) stearate (St) chains. Interestingly, both iron stearates consist of lamellar structures with planes of iron polynuclear complexes (polycations) separated with stearate chains in all-trans conformation. The iron content in polycations was found very different between both iron stearates. Their detailed characterizations indicate that FeSt 2 is mainly composed of [Fe 3 -(μ 3 -O)St 6 · x H 2 O]Cl, with no (or few) free stearate, whereas FeSt 3 is a mixture of mainly [Fe 7 (μ 3 -O(H)) 6 (μ 2 -OH) x St 12-2 x ]St with some [Fe 3 (μ 3 -O)St 6 · x H 2 O]St and free stearic acid. The formation of bigger polynuclear complexes with FeSt 3 was related to higher hydrolysis and condensation rates within the iron(III) chloride solution compared to the iron(II) chloride solution. These data suggested a nucleation mechanism based on the condensation of polycation radicals generated by the catalytic departure of two stearate chains from an iron polycation-based molecule.

Controlled hydration leads to four derivatives of a metal-organic framework consisting of cadmium ions, N 1 , N 1 , N 4 , N 4 -tetrakis(4-(pyridin-4-yl)phenyl)benzene-1,4-diamine, and coordinated and free nitrates. The balance of water coordination and the multitude of bonding of the weakly coordinated nitrate lead to a progressive change in the coordination number of the Cd 2+ ions from eight to seven to six without great perturbation to the 4-fold interpenetration three-dimensional framework.

Layering AgNO 3 in alcohol onto octavinylsilsesquioxane (OVS) in CHCl 3 results in a one-dimensional coordination polymer, {Ag 4 (NO 3 ) 4 (OVS)·solvents} n ( SD/Ag4a-d ), consisting of unprecedented flat weakly bonded Ag 4 (NO 3 ) 4 alternating with the firmly covalent OVS through Ag I -π C═C bonds. The preferential assembling medium for SD/Ag4a is proven to be alcohols, where a 4:1 silver-OVS adduct is detected by electrospray ionization mass spectrometry. The present outcomes may assist our knowledge of particular interactions for supramolecular architectures of a polynuclear silver system built from OVS containing eight pendent olefin tails.

With the aim of developing new molecular theranostic agents, a π-extended Zn(II) porphyrin as photosensitizer for photodynamic therapy (PDT) linked to two GdDOTA-type complexes for magnetic resonance imaging (MRI) detection was synthesized. The relaxivity studies revealed a much higher relaxivity value per Gd ion for this medium sized molecule (19.32 mM -1 s -1 at 20 MHz and 298 K) compared to clinical contrast agents-a value which strongly increases in the presence of bovine serum albumin, reaching 25.22 mM -1 s -1 . Moreover, the photophysical studies showed the strong ability of the molecule to absorb light in the deep red (670 nm, ε ≈ 60000 M -1 cm -1 ) and in the near-infrared following two-photon excitation (920 nm, σ 2 ≈ 650 GM). The conjugate is also able to generate singlet oxygen, with a quantum yield of 0.58 in DMSO. Promising results were obtained in cellular studies, demonstrating that the conjugate is internalized in HeLa cells at micromolar concentration and leads to 70% of cell death following 30 min irradiation at 660 nm. These results confirm the potential of the designed molecule as an imaging and therapeutic agent.

We present an unprecedented copper(II)-assisted organic ligand fragmentation process under basic conditions leading to several ligands within three families of metallamacrocycle, Cu 6 , Cu 8 , and Cu 16 . The sequential multistep reaction include (i) the deprotonation of the starting alcohol, 1,2-bis(3,5-dimethyl-pyrazol-1-yl)ethane-1,2-diol ( H 2 bdped ) to its diolate bdped followed by complexation through six bonds (μ 6 ) to three copper atoms in a ring, (ii) the breaking of the ethane-pyrazole C-N bonds by the different solvent alcohols to form 1-(3,5-dimethyl-pyrazol-1-yl)-2-methoxyethane-1,2-diolate ( dpmed ) or 2-(3,5-dimethyl-pyrazol-1-yl)-2-hydroxyacetate ( dpet ), while retaining coordination to the copper centers and (iii) the final step to ethane-1,1,2,2-tetraolate, C 2 H 2 O 4 4- ( et ). Importantly, the latter product, only observed on two previous occasions, occupies the core of Cu 6 and Cu 16 through exceptionally eight coordination bonds (μ 8 ). Its alkyl esters, 2-alkoxyethane-1,1,2-triolate ( met , eet , and pet ), also occupy the central parts of Cu 8 but forming six bonds (μ 6 ) instead. The other product, 3,5-dimethylpyrazolate ( dp ), acts as peripheral bridges (μ 2 ) but it is not involved in coordination if the starting salt is copper acetate, this may be a consequence of acetate being a better μ 2 -chelating ligand. In the presence of an oxidizing agent, K 2 Cr 2 O 7 , C 2 H 2 O 4 4- ( et ) is oxidized to oxalate, C 2 O 4 2- ( ox ). Thus, an additional μ 3 -hydroxide and μ 4 -oxalate in Cu 16 widen the complexity of the structures, not to mention the range of coordination geometries of the copper centers, though in the present cases they can be classed in only two types: distorted square-planar and square-pyramid. In addition to single-crystal crystallography, the results from different techniques such as IR, ESI-MS, optical UV-vis, and SQUID magnetometry help in the characterization of these rare metallamacrocycles made from unexpected and in situ generated ligands. We believe the results of the organic transformations are highly relevant to von Liebig's benzil-benzilic acid rearrangement.

Dipyrrolyldiketone ligands ( dpk H) are used with Ti(O i Pr) 4 to afford monomeric titanium(IV) complexes displaying the general formula C 2 -[Ti( dpk ) 2 (O i Pr) 2 ]. The dpk H ligands employed consist of two dipyrrolyldiketone compounds ( 2 H and 3 H) and three diphenyl-substituted analogues ( 4 H- 6 H). The behavior of these octahedral [Ti( dpk ) 2 (O i Pr) 2 ] species in solution was investigated by 1 H NMR at variable temperatures. Dynamic phenomena were evidenced, and the activation parameters associated with these processes (Δ H ⧧ , Δ S ⧧ , and Δ G ⧧ ) were retrieved. [Ti( dpk ) 2 (O i Pr) 2 ] complexes are precursors for the formation of high-nuclearity aggregates whose structures depend on the substituents on the diketone backbone. The crystal structures of monomeric ([Ti( 1 ) 2 (O i Pr) 2 ]; 1 is the 1,3-diphenyl-1,3-propanedionato ligand) and [Ti( 2 ) 2 (OEt) 2 ]), dimeric ([Ti 2 ( 1 ) 4 (μ 2 -O) 2 ]), and tetrameric ([Ti 4 ( 4 ) 8 (μ 2 -O) 4 ]) species have been established, and the origin of this structural diversity is discussed. The solid-state optical properties of several complexes were determined and interpreted with the help of DFT calculations. Finally, the dinuclear complex [Ti( 6 ) 2 (μ 2 -O) 2 ] was synthesized, where ligand 6 incorporates six long alkyl chains (C 16 H 33 ). This complex shows rich mesomorphic properties, with an original room-temperature plastic crystal phase followed by a hexagonal columnar liquid-crystalline phase.

The synthesis of monomeric octahedral complexes constructed around a TiO 4 N 2 core bearing neocuproine derivatives is detailed. These architectures follow the [Ti( 1 ) 2 ( N-N )] general formulas, where 1 is the 6,6'-diphenyl-2,2'-biphenolato ligand and N-N is a 1,10-phenanthroline derivative. Single-crystal analysis revealed that the neocuproine-based ligands within these architectures adopt a nonplanar geometry. The distortion of these aromatic diimine systems has been quantified through measurement of a torsion angle (α) and a dihedral angle (β) defined by two planes within the aromatic diimine molecule (π 1 and π 2 ), permitting one to evaluate the twisting and bending of a coordinated nitrogen ligand, respectively. Next, the scope of this investigation was extended to the synthesis of a dimeric architecture, [Ti 2 ( 1 ) 4 ( 3 )], where 3 is the 5,5'-bis(neocuproine) ligand. Again, a strong distortion of the neocuproine fragments was characterized in the crystalline state for such a complex. The UV-visible properties of these complexes were interpreted with the help of time-dependent density functional theory calculations. The solution behavior as well as good hydrolytic stability of these species has been established.

Reaction of the metalloligand Ir III (ppy-COOH) 3 and the anisotropic paramagnetic Co II ion under solvothermal conditions resulted in a metal-metalloligand coordination polymer, [Co II 3 (μ 3 -O)(μ-OH 2 ){Ir III (ppy-COO) 2 (ppy-COOH)} 2 (H 2 O) 4 ]·2DMF· x H 2 O ( I ). It consists of trimeric Co 3 O secondary building units (SBUs) bridged by pairs of Ir to form chains of alternate orthogonal squares. The compound undergoes two single-crystal to single-crystal transformations while retaining its general structural features. A chemical transformation occurs to give [Co II 3 (μ 3 -O){Ir III (ppy-COO) 2 (ppy-COOH)} 2 (H 2 O) 4 (DMF)]·DMF·H 2 O ( II ) by soaking in acetone, where a bridging water molecule departs and the solvent DMF bonds to the vacant site of the Co center. Both I and II undergo a temperature-induced transformation to [Co II 3 (μ 3 -O){Ir III (ppy-COO) 2 (ppy-COOH)} 2 (H 2 O) 3 (DMF)]·DMF ( III ), where one more coordinated water molecule is lost. The major difference in the three phases is in the Co coordination spheres, which have considerable consequences on the magnetism. Compound I displays paramagnetism down to 2 K, whereas II and III show weak ferromagnetism with T C values of 14 and 17 K, respectively.

Understanding and controlling confined nanospace to accommodate substrates and promote high ion conduction are essential to various fields. Layered double hydroxides (LDHs) have emerged as promising candidates for anion exchangers using the interlayer nanospace in their crystal structures. Miyata reported in 1983 that the affinity of anions for intercalation with most major Mg-Al LDHs increased in the following order: NO 3 - < Br - < F - < SO 4 2- < HPO 3 2- . Attempts to alter the affinity with different metal cations (M 2+ and M 3+ ) have been unsuccessful. Analyses of the crystalline structures of LDHs, positively charged host layers, interlayer anions, and interlayer water molecules indicate that they inevitably interact through hydrogen bonding. In other words, the affinity of LDHs for anions is controlled by tuning the hydrogen bonding. In this study, we prepared fluorine-substituted LDHs (F-LDHs) with different Mg/Al ratios by partially replacing the OH structural groups, which originated from the host layer, with fluorine atoms; the resulting change in affinity was investigated. The distribution coefficient, which is a useful indicator of the affinity of an LDH for a particular anion, was examined. The results showed that only F-LDHs with Mg/Al ratios of 3.5 exhibited high affinity, especially for NO 3 - ions, and the affinity increased in the following order: HPO 4 2- < SO 4 2- < F - < Br - < NO 3 - . The separation factors of these specific F-LDHs with respect to both NO 3 - /F - and NO 3 - /SO 4 2- were higher than that of LDHs with other compositions by 1 order of magnitude. Raman spectroscopy above 3000 cm -1 revealed that the fluorine substitution of LDHs significantly changed the hydrogen bonding nature in the interlayer space. Highly electronegative fluorine atoms significantly decrease the extent of hydrogen bonding interactions between OH structural groups and both interlayer water molecules and anions, wherein steric effects are induced by the shrunken interlayer space, and van der Waals forces are revealed to be the predominant interaction with anions. Therefore, the highest affinity was observed for NO 3 - ions in F-LDHs.

When the reaction of zinc nitrate with 4',4‴,4‴″,4‴‴'-(ethene-1,1,2,2-tetrayl)tetrakis[(1,1'-biphenyl-3-carboxylic acid)] (H 4 tmpe) in dimethylformamide (DMF) under hydrothermal condition is performed in air or carbon dioxide (CO 2 ), [Zn 4 (tmpe) 2 (H 2 O) 2 (μ 2 -CO 2 )]·8DMF·18H 2 O ( 1 ) crystallizes out. However, if it is in dioxygen, argon, or carbon monoxide, [Zn 2 (tmpe)(DMF)]·2DMF·8H 2 O ( 2 ) is the product. Both compounds are chemically stable coordination polymers. 1 contains zinc carboxylate paddlewheels as nodes linearly bridged by CO 2 into two interpenetrating lattices, and 2 has an infinite single framework formed by a tetranuclear node. 1 is the second example containing the linear CO 2 -bridged paddlewheel node. Interestingly, CO 2 fixation in a μ 2 -η 2 O,O bridging mode is observed in 1 , which is rarely characterized structurally and has been confirmed using IR and gas chromatography analysis. The stability of 1 is further verified by density functional theory calculations, which found an energy minimum with a Zn-O═C angle of 180°. Both compounds display strong emission around 490 nm and excited-state lifetimes around 2.4 ns.

A mixed-valent hexadecanuclear manganese cluster, [Mn II 2 Mn III 14 (trz) 14 (thetach) 4 (μ 3 -O) 8 (H 2 O) 10 ](ClO 4 ) 6 ( Mn16 ), containing two Mn II and 14 Mn III ions, is constructed from mixed in situ generated ligands, 1,2,3-triazole (Htrz) and 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (H 3 thetach). Remarkably, both ligands were not initially added into the reaction system, and their formations involve the in situ ligand decomposition and subsequent condensation reactions. The core of Mn16 is an elongated torus comprised of eight Mn atoms and four [Mn 2 O 2 ] subunits bridged by oxo or alkoxide. The high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) of Mn16 dissolved in CH 3 CN indicates its structure remains intact as +3 and +4 species. Temperature and field dependent magnetization revealed predominantly antiferromagnetic exchange interactions within the cluster. The work provides one-pot synthesis of high-nuclearity manganese clusters using the ligands generated by in situ reactions in a tandem fashion.

By virtue of its magnetic moment and variable valencies, the D 4 h paddlewheel ruthenium dimer is a desirable molecular building block for the construction of functional networks. If in addition to the Ru open axial site the organic ligand is designed to allow transversal connections, a wider range of structural possibilities is expected. The organic ligand can also be modified to introduce other functionalities. In the present study we employed a diphosphonate containing a protonated amine, 1-ammoniummethylenediphosphonate [NH 3 CH(PO 3 ) 2 3- ; (Hamdp)], as the ligand to construct paddlewheel Ru 2 (Hamdp) 2 building block. Three networks of different structural dimensionalities were obtained. (H 3 O) 2 [Ru II 2 (Hamdp) 2 ] ( 1 ) forms one-dimensional chain of S = 1 Ru II 2 bridged at axial positions through Ru-O bonds. From 1 as a starting material, its reaction with lanthanide ions results in the bimetallic Dy(H 2 O) 3 [Ru 2 (Hamdp) 2 ][Ru 2 (Hamdp) 2 (H 2 O) 2 ][Ru 2 (Hamdp)(amdp)] 0.5 ·12H 2 O ( 2 ), which has a pillared-bilayer structure and Yb[Ru 2 (Hamdp) 2 ] 2 [Ru 2 (Hamdp) 2 (H 2 O) 2 ]·15H 2 O ( 3 ), which is a three-dimensional open framework, both contain mixed-valent Ru II/III 2 units and show new connection topologies of the Ru 2 dimers. After activation 2 does not adsorb N 2 and CO 2 but takes up 12 H 2 O. In contrast, 3 take up all three gases. The optimum proton conductivities were moderate reaching 1.44 × 10 -6 for 2 and 0.93 × 10 -5 S cm -1 for 3 at 95% relative humidity and 55 °C.

In search of multifunctional metal-organic frameworks (MOFs), redox-active donors and acceptors, namely, tetrathiafulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), were concomitantly used as skeletal components with diamagnetic metal nodes (Cd and Zn) to construct unique framework materials. Six isostructural frameworks were synthesized by diffusion of metal salts, TTF(py) 4 , and either paramagnetic Li(TCNQ) or diamagnetic H 2 TCNQ. They were characterized by single-crystal X-ray diffraction and FT-IR and UV-vis-NIR spectroscopy, and their physical properties were studied, including two postsynthetic modifications involving crystal-to-crystal transformations following a solid-solution reaction with I 2 . The highly colored crystals of two isostructural Zn and Cd frameworks contain undulating Cd-TTF(py) 4 layers entwined with TCNQ in a chicken-wire net as part of the skeleton of the MOF as well as TCNQ intercalated within the channels, while nitrate anions are occluded within the cavities formed by the pyridine moieties. Reaction with I 2 replaces each intercalated TCNQ •- within the channels with I 3 - . The optical properties and the electron paramagnetic resonance (EPR) spectra indicate the presence of only radical TCNQ •- in the parent compounds, while the magnetic susceptibilities enabled an estimation of the amount of TCNQ •- ( S = 1/2) leading to almost paramagnetic behavior. Solid-state electrochemistry provides evidence of several one-electron redox states corresponding to the electroactive cores.

The luminescent properties of gold(I)-sulfur compounds have received much attention for their potential applications in the sensing field. The molecular level regulation of luminescence remains a challenge. It is critical to unravel the relationship between the luminescence and the structure. Herein we report a binuclear complex [Au 2 (dppaptc) 2 ]Cl 2 (1, dppaptc = N,N-bis(diphenylphosphanylmethyl)-amino-4-phenyl-thiocarbamide), which exhibits variations at Au-S bond lengths as a function of temperature or solvent. X-ray analysis reveals a linear decrease from 2.900(3) to 2.745(15) Å upon cooling 1·2CHCl 3 from 300 to 80 K combined with a linear correlation with its luminescence intensity at 475 nm, which was confirmed by TD-DFT calculations. Compound 1, if solvated with H 2 O and alcohol, possesses the shorter Au-S bonds and enhanced luminescence. The close relationship between luminescence intensity and Au-S length serves as a complement to existing luminescent gold(I)-sulfur systems and provides some insight into understanding the thermochromism and solvatochromism of the gold(I)-sulfur compounds.

Three new copper(I) complexes [Cu(L X ) 2 ] + (PF 6 - ) (where L X stands for 2,9-dihalo-1,10-phenanthroline and X = Cl, Br, and I) have been synthesized in order to study the impact of halogen substituents tethered in the α position of the chelating nitrogen atoms on their physical properties. The photophysical properties of these new complexes (hereafter named Cu-X) were characterized in both their ground and excited states. Femtosecond ultrafast spectroscopy revealed that early photoinduced processes are faster for Cu-I than for Cu-Cl or Cu-Br, both showing similar behaviors. Their electronic absorption and electrochemical properties are comparable to benchmark [Cu(dmp) 2 ] + (where dmp stands for 2,9-dimethyl-1,10-phenanthroline); furthermore, their optical features were fully reproduced by time-dependent density functional theory and ab initio molecular dynamics calculations. All three complexes are luminescent at room temperature, showing that halogen atoms bound to positions 2 and 9 of phenanthroline are sufficiently bulky to prevent strong interactions between the excited Cu complexes and solvent molecules in the coordination sphere. Their behavior in the excited state, more specifically the extent of the photoluminescence efficiency and its dependence on the temperature, is, however, strongly dependent on the nature of the halogen. A combination of ultrafast transient absorption spectroscopy, temperature-dependent steady-state fluorescence spectroscopy, and computational chemistry allows one to gain a deeper understanding of the behavior of all three complexes in their excited state.

It was shown that His3 of human copper transporter 1 (hCtr1) prompts the ATCUN-like Cu(II) coordination for model peptides of the hCtr1 N-terminus. Its high Cu(II) affinity is a potential driving force for the transfer of Cu(II) from extracellular Cu(II) carriers to hCtr1. Having a sequence similar to that of hCtr1, hCtr2 has been proposed as another human copper transporter. However, the N-terminal domain of hCtr2 is much shorter than that of hCtr1, with different copper binding motifs at its N-terminus. Employing a model peptide of the hCtr2 N-terminus, MAMHF-am, we demonstrated that His4 provides a unique pattern of Cu(II) complexes, involving Met sulfurs in their Cu(II) coordination sphere. The affinity of Cu(II) for MAMHF-am is a few orders of magnitude lower than that reported for the hCtr1 model peptides at the extracellular pH of 7.4, suggesting a maximal complementary role of Cu(II) binding to hCtr2 in the import of copper from the extracellular space to the cytoplasm. On the other hand, the ability of the hCtr2 model peptide to capture Cu(II) from amino acids and short peptides (potential degradation products of proteins) at pH 5.0 and the known predominant lysosomal localization of hCtr2 support an important potential role of the Cu(II)-hCtr2 interaction in the recovery of copper from lysosomes.

Two trinuclear Cu II pyrazolato complexes with a Cu 3 (μ 3 -E)-core (E = O 2- or OH - ) and terminal nitrite ligands in two coordination modes were characterized crystallographically, spectroscopically, and electrochemically. One-electron oxidation of the μ 3 -O species produces a delocalized, mixed-valent, formally Cu II 2 Cu III -nitrite, but no nitrate. In contrast, under reducing conditions-addition of PhSH as an electron and proton donor-both complexes mediate the reduction of nitrite, releasing NO.

The solvothermal reaction of cobalt(II) sulfate with S, S-1,2- bis(1-methyl-1 H-benzo[ d]imidazol-2-yl)ethane-1,2-diol, (H 2 L), neutralized with triethylamine (Et 3 N) in a mixture of methanol and water (2:1), resulted in triangular red crystals of [Co II 7 (L) 3 (SO 4 ) 3 (OH) 2 (H 2 O) 9 ]·4H 2 O·3CH 3 OH (Co 7 ). It is formed of chiral and polar clusters crystallizing in the R 3 space group. Co 7 consists of apex-shared asymmetric dicubane units where all of the metals adopt an octahedral coordination and the three ligands wrap diagonally around the unit. One end of the cluster is bonded by six water molecules and the other end by three monodentate sulfates. The head-to-tail packing through extended H-bonds leads to polar chains. The ligand has lost two protons, adopts a cis-conformation, and is coordinated to five metals around the waist of the dicubane. Electrospray ionization mass spectrometry (ESI-MS) of solutions of the reaction as a function of time reveals the possible step-by-step assembly process of the cluster: the initial product [Co II (HL)(SO 4 )] 2- combines with CoSO 4 , forming [Co II 2 (HL)(SO 4 ) 2 ] 2- , and then, upon addition of Et 3 N, dimerizes through a [OH] - bridge to [Co II 4 (HL) 2 (OH)(CH 3 OH) 2 (SO 4 ) 3 ] - followed by capture of one Co 2+ and one CoSO 4 to form [Co II 6 (L) 2 (OH)(CH 3 O)(SO 4 ) 4 ] 2- before eventually binding to CoL to form [Co II 7 (L) 3 (OH) 2 (SO 4 ) 4 ] 2- . These results allow us to propose a possible process for the formation of Co 7 , which is a good example for chiral multidentate chelating ligand-controlled assembly of clusters. Magnetization measurements as a function of the temperature, field, and ac-frequency reveal ferromagnetic coupled moments and single-molecule magnetism (SMM).

The search for functional materials, for example those aiming at microelectronics, magnetic recording, and catalysis, often ventures into mixed metal systems to achieve optimization of the properties. Thus, understanding site preference and self-organization is crucial but hard to implement. Herein, we present a system whereby Mg II , Mn II , and Mn III ions selectively locate exact positions within the Brucite-structured cluster, Mn 13 Mg 6 , [Mn III ⊂Mg II 6 ⊂Mn II 9 Mn III 3 ( L) 18 (OH) 12 (N 3 ) 6 ](ClO 4 ) 6 ·12CH 3 CN, H L = 1-(hydroxymethyl)-3,5-dimethylpyrazolate). The Mn III being small (78 pm) takes up the core position; while 6 Mg II (86 pm) are located in the inner ring, and the 9 large Mn II (97 pm) and 3 Mn III occupy the outer ring. The factors (a) ionic radii, (b) regularity in coordination geometry, oxophilicity, and softness of Mg II compared to Mn II , and (c) Jahn-Teller distortion of Mn III may all be implicated synergistically. Electrospray ionization mass spectrometry reveals the M 19 disc remains an integral unit when crystals are dissolved, and exchange between Mg and Mn occurs within the disc during its formation. Diamagnetic Mg II doping insulates the magnetic exchange between the central Mn III and those in the outer ring, thus giving an overall antiferromagnetic exchange interaction between nearest-neighbors of the outer ring. The work reveals the underlying rule for site-preference of main group metal versus transition metal in disc-like Brucite-structured cluster and provides an elegant new avenue to assemble heterometallic clusters in a stepwise fashion.

Reactions of the phosphanyl-gold(I) precursor [(AuCl) 2 (bdppmapy)] (1; bdppmapy = N,N-bis(diphenylphosphanylmethyl)-2-aminopyridine) with Na 2 S in a 1:1 or 1:2 molar ratio gave rise to one tetradecanuclear and one octanuclear Au(I) sulfido cluster, [Au 14 S 6 (bdppmapy) 5 ]Cl 2 (2) and [Au 18 S 8 (bdppmapy) 6 ]Cl 2 (3), respectively. The former displays a new structural framework in gold cluster chemistry. Compounds 2 and 3 showed strong green luminescence and were employed as excellent imaging probes to selectively light up the lysosomes of living cells. Their long-term tracking of lysosomes can be achieved for up to 36 h, while tracking with commercial Lyso-Tracker Red under the same conditions was limited to 3 h. Our work demonstrated the possibility of constructing novel gold(I) sulfido clusters supported by special P-N hybrid ligands and the potential application of these clusters as long-term selective trackers of lysosomes in bioimaging.

Metal-organic frameworks (MOFs) incorporating lanthanide nodes and tetrathiafulvalene (TTF) linkers offer a viable approach for combining redox activity and magnetism in one material. Four rare-earth lanthanide ions (RE = Tb, Dy, Ho, and Er) were found to form isostructural MOFs consisting of metal chains bridged by redox-active tetrathiafulvalene-tetrabenzoate (TTFTB 4- ) whereby the carboxylate moieties act in both anti- anti and syn- syn coordination modes. These materials display tunable redox-active properties and slow magnetic relaxation phenomenon (Er and Dy). While the as-synthesized crystals contain the neutral diamagnetic TTF moiety, using either a solid-solution electrochemical method or iodine oxidation transforms part of the latter to the paramagnetic TTF •+ radical in a single-crystal-to-single-crystal manner without altering the internal structure of the building chains and the frameworks. This is accompanied by inclusion of I 3 - replacing some of the solvents, as well as changes in the central C-C bond length of TTFTB, a strong EPR response at g ∼ 2, and an enhancement of the reflectance at low energies originating from absorption by the radical.

The subtle balance of the metrics of the highly supple 5,5'-pyridyl-3,3'-bis-1 H-pyrazolate and the variable coordination numbers of Cu(I) favor the stabilization of a [4 × 4] grid complex with all Cu(I). It has numerous cuprophilic bonds (Cu···Cu = 2.56-3.02 Å), and consequently, exhibits strong orange luminescence that fades upon insertion of solvents without loss of crystallinity.

Magnetic susceptibility and X-band electron paramagnetic resonance (EPR) studies have been carried out on the highly symmetric [Cr 3 O(PhCOO) 6 (py) 3 ](ClO 4 )·0.5py (1; py = pyridine), whose cation exhibits a D 3 h crystallographically imposed molecular symmetry. While magnetic susceptibility data can be interpreted with an equilateral magnetic model described by the effective multispin Hamiltonian Ĥ = -2 J(Ŝ 1 ·Ŝ 2 + Ŝ 2 ·Ŝ 3 + Ŝ 3 ·Ŝ 1 ), EPR data require an isosceles model described by the multispin Hamiltonian Ĥ = -2 J( Ŝ 1 · Ŝ 2 + Ŝ 2 · Ŝ 3 ) - 2 J' Ŝ 3 · Ŝ 1 , where Δ J = J - J' ≠ 0. Moreover, EPR data reveal the interplay of antisymmetric exchange (or Dzyaloshinskii-Moriya) interactions, described by a 2G(Ŝ 1 × Ŝ 2 + Ŝ 2 × Ŝ 3 + Ŝ 3 × Ŝ 1 ) term, which induce significant anisotropy to the S T = 1 / 2 ground state of 1, as well as an important broadening of the g ⊥ resonance ( g strain). Through careful analysis of these data and in conjunction with neutron scattering data, this g strain can be deconvoluted into distributions of the individual spin-Hamiltonian parameters Δ J and |G|. This method of analysis provides simultaneous estimates of the central values and distribution profiles of the spin-Hamiltonian parameters, which are shown not to be described by monodisperse values.

We previously reported that the [Rh III (dmbpy) 2 Cl 2 ] + (dmbpy = 4,4'-dimethyl-2,2'-bipyridine) complex is an efficient H 2 -evolving catalyst in water when used in a molecular homogeneous photocatalytic system for hydrogen production with [Ru II (bpy) 3 ] 2+ (bpy = 2,2'-bipyridine) as photosensitizer and ascorbic acid as sacrificial electron donor. The catalysis is believed to proceed via a two-electron reduction of the Rh(III) catalyst into the square-planar [Rh I (dmbpy) 2 ] + , which reacts with protons to form a Rh(III) hydride intermediate that can, in turn, release H 2 following different pathways. To improve the current knowledge of these key intermediate species for H 2 production, we performed herein a detailed electrochemical investigation of the [Rh III (dmbpy) 2 Cl 2 ] + and [Rh III (dtBubpy) 2 Cl 2 ] + (dtBubpy = 4,4'-di- tert-butyl-2,2'-bipyridine) complexes in CH 3 CN, which is a more appropriate medium than water to obtain reliable electrochemical data. The low-valent [Rh I (Rbpy) 2 ] + and, more importantly, the hydride [Rh III (Rbpy) 2 (H)Cl] + species (R = dm or dtBu) were successfully electrogenerated by bulk electrolysis and unambiguously spectroscopically characterized. The quantitative formation of the hydrides was achieved in the presence of weak proton sources (HCOOH or CF 3 CO 3 H), owing to the fast reaction of the electrogenerated [Rh I (Rbpy) 2 ] + species with protons. Interestingly, the hydrides are more difficult to reduce than the initial Rh(III) bis-chloro complexes by ∼310-340 mV. Besides, 0.5 equiv of H 2 is generated through their electrochemical reduction, showing that Rh(III) hydrides are the initial catalytic molecular species for hydrogen evolution. Density functional theory calculations were also performed for the dmbpy derivative. The optimized structures and the theoretical absorption spectra were calculated for the initial bis-chloro complex and for the various rhodium intermediates involved in the H 2 evolution process.

Spin-crossover (SCO) molecular solids are valued switchable materials for their common abrupt and reversible thermal transitions, large thermal hysteresis, or guest-dependent effects. These properties usually involve crystallographic transitions coupled to the SCO events. These phenomena are of great value for the understanding of solid-state transformations and also for exploiting them. We present here a lattice of the complex [FeL(bbp)](ClO 4 ) 2 (1; L and bbp are tris-imine ligands) featuring an unprecedented rich succession of SCO and crystallographic phase transformations. Magnetometry measurements unveil a thermally irreversible sequence of spin conversions that delineate four different thermal pathways. All of these are single-crystal-to-single-crystal processes and can thus be monitored by single crystal X-ray diffraction using one unique specimen. Fresh crystals of 1 contain one molecule of acetone per Fe center (1·ac) that abandons the lattice upon warming at the same time that a SCO from an ordered mixed spin state (1:1 high spin/low spin; HS/LS) to a fully HS state, 1 α , occurs. This crystallographic phase, accessed through a template effect by the solvent, converts into another one, 1 β , upon cooling, as triggered by a HS to LS SCO. Warming of 1 β induces a new SCO (LS to ordered HS/LS) coupled to another crystallographic phase transition, 1 β → 1 γ . The fully HS state of 1 γ can not be reached before decomposition of the compound. Instead, this phase cycles between the HS/LS and the LS states through superimposable pathways, different from that of the prerequired 1 β → 1 γ phase change. Analysis of the thermal variation of the free energy, G, through density functional theory methods provides trends in agreement with the observation of these transformations and clarifies the possible metastable nature of the various phases identified. This unique behavior allows the access to four different magnetic responses depending on the thermal history of the sample, within a given range of temperatures near the ambient conditions.

A bromonium oxidizing agent was used to produce a ring-oxidized zinc phthalocyanine (PcZn), [PcZn(solvent)] • 2 [BAr F 4 ] 2 (1·solvent), in good yield. This material is dimeric in the solid state with one axially coordinated solvent [tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME)] and close intradimer ring-ring distances of 3.18 and 3.136 Å (THF and DME respectively); this proximity facilitates strong antiferromagnetic coupling to yield diamagnetic dimers. 1·THF is present in solution as a monomer and a dimer. In CH 2 Cl 2 , the dimer is favored above 0.1 mM, and it is almost exclusively present in solvents with a high dielectric constant such as acetonitrile. The material 1·THF/DME decomposes in DME to a meso-nitrogen-protonated species, [HPcZn(DME) 2 ][BAr F 4 ] (2), which was isolated and represents the first example of such a structurally characterized, protonated, unsubstituted PcM complex. A partially oxidized dimer or "pimer" [(PcZn(DME)) 2 ] • [BAr F 4 ] (3) was also structurally characterized and has a intradimer ring-ring distance of 3.192 Å, similar to 1·THF/DME. Dimer 3 also represents the first isolated PcM-based pimer. Electron paramagnetic resonance analysis of a 1.0 mM solution of 1·DME in DME showed the production of 3 over hours by the combination of 1·DME and 2 in solution.

Cooperativity is key in defining the shape (i.e., gradual, abrupt, or hysteretic) of thermally driven spin transitions in magnetic switches. Despite its importance, there is very little information on its atomistic origin, which hinders the rational design of materials displaying a bistability region (i.e., hysteresis). In this paper, we investigate the spin transition of two solvatomorphs of [Fe(2-pic) 3 ]Cl 2 , an Fe(II)-complex displaying thermal spin crossover (SCO) from a low-spin (LS) to a high-spin (HS) state with either gradual or abrupt two-step character. To do it, we apply a novel computational protocol to study the cooperativity of SCO compounds from DFT calculations, which does not rely on a priori assumptions on the studied system. The distinct shape of the spin transition is successfully captured, and the atomistic origin of cooperativity is traced back to geometrical distortions of the Fe-N 6 core in case of the solvatomorph exhibiting an abrupt transition. According to our calculations, HS and LS molecules contribute differently to cooperativity, which results in a complex energetic evolution of the spin transition that cannot be described by the common Slichter-Drickamer model. The present work opens new avenues for the study of cooperativity of SCO systems having a chemically oriented perspective and demonstrates that quantum chemistry calculations can discriminate the shape of a spin transition, while providing insight into the atomistic underlying factors that contribute to its cooperative behavior.

Three polyoxometalates (POMs) functionalized by tetrathiafulvalene (TTF) molecules have been synthesized by a coupling reaction between the Anderson-type POMs [MnMo 6 O 18 {(OCH 2 ) 3 CNH 2 } 2 ] 3- or [AlMo 6 O 18 (OH) 3 {(OCH 2 ) 3 CNH 2 }] 3- and the TTF carboxylic acid derivative (MeS) 3 TTF(S-CH 2 -CO 2 H). The monofunctionalized TTF-AlMo 6 POM contains one TTF group covalently grafted on an Al Anderson platform. The symmetrical TTF-MnMo 6 -TTF POM possesses two TTF groups grafted on each side of a Mn Anderson derivative while the asymmetrical TTF-MnMo 6 -SP POM contains a TTF and a spiropyran groups. These three trianionic species have been characterized by elemental analysis, 1 H and 13 C NMR, FT-IR spectroscopy, ESI-MS spectrometry, and single-crystal X-ray diffraction (for TTF-MnMo 6 -TTF). In the solid state, the grafted TTF molecules of TTF-MnMo 6 -TTF POMs interact via S···S and π···π interactions and form chains. The electrochemical properties of the complexes reflect the contributions of both the inorganic POM and the TTF moieties. Despite adsorption of the oxidized hybrid species on the Pt grid working electrode, UV-vis-NIR spectroelectrochemical investigations evidence peaks characteristic of the oxidation of the TTF units. Finally, hyper-Rayleigh scattering (HRS) measurements show that the three novel TTF derivatives exhibit β values between 20 and 37 × 10 -30 esu. Moreover it is observed that the oxidation of the TTF moieties by Fe 3+ ions increases the NLO response. These values are in the order of magnitude of that found for the well-known 4-dimethylamino- N-methyl-4-stilbazolium (DAS + ) cation (β = 60 × 10 -30 esu).

A new design concept has been realized for the construction of molecular conductors, whereby the building unit contains a core reservoir of carriers made up of metal ions with controllable valence states and shelled by flat organic ligands having an extended π-system to promote supramolecular electronic communication. Therefore, reacting the conjugated multidentate ligand 5,5'-pyridyl-3,3'-bi-1 H-pyrazole with different copper salts solvothermally led to three interesting hexameric salts having different ground-state valences, [Cu II 6 (L) 4 (NO 3 )(CH 3 OH) 2 ](NO 3 ) 3 ·4CH 3 OH, [(CH 3 ) 2 NH 2 ][Cu I Cu II 5 (L) 4 ](SO 4 ) 2 ·4H 2 O, and [Cu I 2 Cu II 4 (L) 4 ](NO 3 ) 2 ·2CH 3 OH. The monovalent Cu II 6 salt is an insulator, but the mixed-valent Cu II 5 -Cu I and Cu II 4 -Cu I 2 salts are semiconductors. Magnetic exchange interactions up to J NN = -158 cm -1 dominate the susceptibilities and lead to ground-state spin S T = 1 (Cu II 6 ), 1/2 (Cu II 5 -Cu I ), and 0 (Cu II 4 -Cu I 2 ) at 40 K. Cyclic voltammetry shows the stepwise one-electron oxidation-reduction through all the possible valence states. The theoretical calculations of the electronic and band structures of the three compounds substantiate the experimentally observed physical properties.

Several porphyrin dimers linked by metal ions were prepared. One trimeric compound was also isolated and one porphyrin dimer linked by palladium(II) could be structurally characterized. In solution, the size of the new compounds was estimated by DOSY NMR techniques. These compounds all contained long aliphatic chains (O-C 12 H 25 ), which were used to assemble them at a highly oriented pyrolytic graphite (HOPG)/liquid interface. The highly ordered arrays were visualized by scanning tunneling microscopy (STM).

Peptides and proteins with the N-terminal motifs NH 2 -Xxx-His and NH 2 -Xxx-Zzz-His form well-established Cu(II) complexes. The canonical peptides are Gly-His-Lys and Asp-Ala-His-Lys (from the wound healing factor and human serum albumin, respectively). Cu(II) is bound to NH 2 -Xxx-His via three nitrogens from the peptide and an external ligand in the equatorial plane (called 3N form here). In contrast, Cu(II) is bound to NH 2 -Xxx-Zzz-His via four nitrogens from the peptide in the equatorial plane (called 4N form here). These two motifs are not mutually exclusive, as the peptides with the sequence NH 2 -Xxx-His-His contain both of them. However, this chimera has never been fully explored. In this work, we use a multispectroscopic approach to analyze the Cu(II) binding to the chimeric peptide Ala-His-His (AHH). AHH is capable of forming the 3N- and 4N-type complexes in a pH dependent manner. The 3N form predominates at pH ∼ 4-6.5 and the 4N form at ∼ pH 6.5-10. NMR experiments showed that at pH 8.5, where Cu(II) is almost exclusively bound in the 4N form, the Cu(II)-exchange between AHH or the amidated AHH-NH 2 is fast, in comparison to the nonchimeric 4N form (AAH). Together, the results show that the chimeric AHH can access both Cu(II) coordination types, that minor changes in the second (or further) coordination sphere can impact considerably the equilibrium between the forms, and that Cu kinetic exchange is fast even when Cu-AHH is mainly in the 4N form.

The preparation and properties of novel ruthenium carbon-rich complexes [(Ph-C≡C-) 2-n Ru(dppe) 2 (-C≡C-bipyM(hfac) 2 ) n ] (n = 1, 2; M = Cu II , Mn II ; bipy = 2,2'-bipyridin-5-yl) characterized by single-crystal X-ray diffraction and designed for molecular magnetism are reported. With the help of EPR spectroscopy, we show that the neutral ruthenium system sets up a magnetic coupling between two remote paramagnetic Cu II units. More specifically, these copper compounds are unique examples of bimetallic and linear heterotrimetallic compounds for which a complete rationalization of the magnetic interactions could be made for exceptionally long distances between the spin carriers (8.3 Å between adjacent Cu and Ru centers, 16.6 Å between external Cu centers) and compared at two different redox states. Surprisingly, oxidation of the ruthenium redox-active metal coupling unit (MCU), which introduces an additional spin unit on the carbon-rich part, leads to weaker magnetic interactions. In contrast, in the simpler parent complexes bearing only one paramagnetic metal unit [Ph-C≡C-Ru(dppe) 2 -C≡C-bipyCu(hfac) 2 ], one-electron oxidation of the ruthenium bis(acetylide) unit generates an interaction between the Cu and Ru spin carriers of magnitude comparable to that observed between the two far apart Cu ions in the above corresponding neutral trimetallic system. Evaluation and rationalization of this coupling with theoretical tools are in rational agreement with experiments for such complex systems.

Information of solid-state and solution structures is crucial in the characterization of molecular clusters and in advancing the understanding of their diverse properties. [Et 3 NH] 2 [Zn 14 (hmq) 8 (OH) 4 X 10 ] [X = Cl and Br; H 2 hmq = 2-(hydroxymethyl)quinolin-8-ol] consist of a peanut-shaped Zn 10 O 12 core, in which the Zn atoms occupy the faces and corners of an octahedron and are protected by bonded halogen atoms and bulky organic ligands. Observation of the [Zn 14 (hmq) 8 (OH) 4 X 10 ] 2- fragment in electrospray ionization mass spectrometry (ESI-MS) suggests that the cluster is stable in solution. ESI-MS analyses from dissolved crystals and mother liquors reveal that Zn(hmq) self-assembles to Zn 5 (hmq) 4 Cl, then dimerizes through four [OH] - bridges to Zn 10 (hmq) 8 (OH) 4 Cl 2 , and progressively captures four ZnCl 2 one-by-one to [Zn 14 (hmq) 8 (OH) 4 Cl 10 ] 2- . Because the supramolecular interactions between the anion and cation in the solid suppress the rotation/vibration of the halogen atoms and confine the movable organic ligands on the rigid Zn-O core, both crystal phases exhibit intense photoluminescence, much stronger than that in solution. This is the first coordination cluster to exhibit "aggregation-induced enhanced emission". In addition, preliminary tests indicate that these coordination clusters are promising for organic-light-emitting-diode applications.

Decoding the principles of cluster-based framework assembly at the molecular level remains a persistent challenge. Herein, we isolated and characterized a novel water-stable three-dimensional (3D) metal-organic open framework [Cl@Ag 14 (cPrC≡C) 10 Cl 2 ·(p-TOS)·1/3H 2 O] n (SD/Ag14, cPrC≡CH = cyclopropylacetylene; p-TOS = p-toluenesulfonate), which contains a chloride-templated Ag 14 cluster as building block. For SD/Ag14, one chloride acts as the template to shape the Ag 14 cluster and the other bridges the clusters to a 3D pcu-h open framework. As revealed by high resolution electrospray mass spectrometry (HRESI-MS), the Ag 12 -Ag 14 species are potential cluster-based intermediates to the 3D pcu-h framework, which authenticates a preconceived idea that the 3D framework is hierarchically assembled from the silver clusters as observed in solid state. Interestingly, SD/Ag14 can be used effectively to remove the environmental pollutant Cr 2 O 7 2- from wastewater through anion exchange in a single-crystal-to-single-crystal (SC-SC) transformation fashion. Furthermore, SD/Ag14 exhibits excellent antibacterial activity against Staphylococcus aureus, thus making it a potential antibacterial agent.

The wide diversity in the structure, pore size, high surface area, adsorption affinity, and selective penetration renders metal-organic frameworks (MOF) attractive as highly efficient adsorbents for chromatographic separation. We report the results of chromatographic separation of four families of biochemically important compounds, viz., linear alkyl hydrocarbons (aldehyde, acid, and ketone), aromatic hydrocarbons (aldehyde, acid, and alcohol), cyclic hydrocarbons (ketone, alcohol, and ester) and aromatic hydrocarbons (ether, ester, and ester with alcohol) with two phenyls, employing the porous MOF [Zn 2 (bdc)(l-lac)] (l-lac = l-lactate; bdc = 1,4-benzenedicarboxylate) as the retention material of the capillary column. Its good performance relies on the robustness and chemical and thermal stability of the framework, the permanent porosity, and, most importantly, the host-guest interaction sites. The results from this work will also help in understanding the intermolecular forces based on host-guest interaction between the MOF and analytes.

Atom economic in situ domino N-alkylation reactions of triethylamine/ammonia with 2-(hydroxymethyl)quinolin-8-ol (HL-OH) assisted by FeSO 4 ·7H 2 O were realized under mild solvothermal conditions at 120 °C in acetonitrile. The resulting tripodal 2,2',2″-[nitrilotris(methylene)]tris(quinolin-8-ol) (H 3 L 3 -N) forms a linear trimer [Fe 3 (L 3 -N) 2 ] (1). Electrospray ionization mass spectrometry of the reaction solution provides evidence for the intermediates of three steps, while crystallography and X-ray photoelectron spectroscopy characterize the trimer. Shortening the time of the reaction allowed for the organic intermediates to be isolated, which led to a proposed mechanism. The method provides a facile way to produce symmetric tertiary amine from widely used NEt 3 and NH 3 . The results represent an example of the in situ Fe 2+ -catalyzed domino reaction in which Fe 2+ is coordinated by the generated ligands and is involved in each step until the final cluster 1.