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The first use of the organic chelate N -hydroxy-1,8-naphthalimide (hynadH) in Dy III chemistry has unveiled access to a synthetic 'playground' composed of four new dinuclear complexes, all of which possess the same planar {Dy 2 (μ-OR) 2 } 4+ diamond-shaped core, resulting from the bridging and chelating capacity of the hynad - groups. The structural stability of the central {Dy 2 } core has allowed for the modulation of the peripheral coordination sites of the metal ions, and specifically the NO 3 - /hynad - ratio of capping groups, thus affording the compounds [Dy 2 (hynad) 2 (NO 3 ) 4 (DMF) 2 ] (1), (Me 4 N) 2 [Dy 2 (hynad) 2 (NO 3 ) 6 ] (2), [Dy 2 (hynad) 4 (NO 3 ) 2 (H 2 O) 2 ] (3), and [Dy 2 (hynad) 6 (H 2 O) 2 ] (4). Because of the chemical and structural modifications in the series 1-4, the Dy III coordination polyhedra are also dissimilar, comprising the muffin (1 and 3), tetradecahedral (2), and spherical tricapped trigonal prismatic (4) geometries. Complexes 1, 2, and 4 exhibit a ferromagnetic response at low temperatures, while 3 is antiferromagnetically coupled. All compounds exhibit out-of-phase ( χ '' M ) ac signals as a function of ac frequency and temperature, thus behaving as single-molecule magnets (SMMs), in the absence or presence of applied dc fields. Interestingly, the hynad - -rich and nitrato-free complex 4, demonstrates the largest energy barrier ( U eff = 69.62(1) K) for the magnetization reversal which is attributed to the presence of the two axial triangular faces of the spherical tricapped trigonal prism by the negatively charged O-atoms of the hynad - ligands.

Reaction of the nitrosylated-iron metallodithiolate ligand, paramagnetic (NO)Fe(N 2 S 2 ), with [M(CH 3 CN) n ][BF 4 ] 2 salts (M = Ni II , Pd II , and Pt II ; n = 4 or 6) affords di-radical tri-metallic complexes in a stairstep type arrangement ([FeMFe] 2+ , M = Ni, Pd, and Pt), with the central group 10 metal held in a MS 4 square plane. These isostructural compounds have nearly identical ν (NO) stretching values, isomer shifts, and electrochemical properties, but vary in their magnetic properties. Despite the intramolecular Fe⋯Fe distances of ca. 6 Å, antiferromagnetic coupling is observed between {Fe(NO)} 7 units as established by magnetic susceptibility, EPR, and DFT studies. The superexchange interaction through the thiolate sulfur and central metal atoms is on the order of Ni II < Pd II ≪ Pt II with exchange coupling constants ( J ) of -3, -23, and -124 cm -1 , consistent with increased covalency of the M-S bonds (3d < 4d < 5d). This trend is reproduced by DFT calculations with molecular orbital analysis providing insight into the origin of the enhancement in the exchange interaction. Specifically, the magnitude of the exchange interaction correlates surprisingly well with the energy difference between the HOMO and HOMO-1 orbitals of the triplet states, which is reflected in the central metal's contribution to these orbitals. These results demonstrate the ability of sulfur-dense metallodithiolate ligands to engender strong magnetic communication by virtue of their enhanced covalency and polarizability., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A combination of inelastic neutron scattering (INS), far-IR magneto-spectroscopy (FIRMS), and Raman magneto-spectroscopy (RaMS) has been used to comprehensively probe magnetic excitations in Co(AsPh 3 ) 2 I 2 ( 1 ), a reported single-molecule magnet (SMM). With applied field, the magnetic zero-field splitting (ZFS) peak (2 D ') shifts to higher energies in each spectroscopy. INS placed the ZFS peak at 54 cm -1 , as revealed by both variable-temperature (VT) and variable-magnetic-field data, giving results that agree well with those from both far-IR and Raman studies. Both FIRMS and RaMS also reveal the presence of multiple spin-phonon couplings as avoided crossings with neighboring phonons. Here, phonons refer to both intramolecular and lattice vibrations. The results constitute a rare case in which the spin-phonon couplings are observed with both Raman-active ( g modes) and far-IR-active phonons ( u modes; space group P 2 1 / c , no. 14, Z = 4 for 1 ). These couplings are fit using a simple avoided crossing model with coupling constants of ca. 1-2 cm -1 . The combined spectroscopies accurately determine the magnetic excited level and the interaction of the magnetic excitation with phonon modes. Density functional theory (DFT) phonon calculations compare well with INS, allowing for the assignment of the modes and their symmetries. Electronic calculations elucidate the nature of ZFS in the complex. Features of different techniques to determine ZFS and other spin-Hamiltonian parameters in transition-metal complexes are summarized.

Volatile lanthanide coordination complexes are critical to the generation of new optical and magnetic materials. One of the most common precursors for preparing volatile lanthanide complexes is the hydrate with the general formula Ln(hfac) 3 (H 2 O) x ( x = 3 for La-Nd, x = 2 for Sm) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato). We have investigated the synthesis of Ln(hfac) 3 (H 2 O) x using more environmentally sustainable mechanochemical approaches. Characterization of the products using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, elemental analysis, and powder X-ray diffraction shows substantial differences in product distribution between methods. The mechanochemical synthesis of the hydrate complexes leads to a variety of coordination compounds including the expected hydrate product, the known retro-Claisen impurity, and hydrated protonated Hhfac ligand depending on the technique employed. Surprisingly, 10-coordinate complexes of the form Na 2 Ln(hfac) 5 ·3H 2 O for Ln = La-Nd were also isolated from reactions using a mortar and pestle. The electrostatic bonding of lanthanide coordination complexes is a challenge for obtaining reproducible reactions and clean products. The reproducibility issues are most acute for the large, early lanthanides whereas for the mid to late lanthanides, reproducibility in terms of product distribution and yield is less of an issue because of their smaller size and greater charge to radius ratio. Ball milling increases reproducibility in terms of generating the desired Ln(hfac) 3 (H 2 O) x along with hydrated Hhfac (tetraol) and free Hhfac products. The results illustrate the dynamic behavior of lanthanide complexes in solution and the solid state as well as the structural diversity available to the early lanthanides.

Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single-molecule magnets (SMMs). Spin-phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits. Direct observation of magnetic transitions and spin-phonon coupling in molecules is challenging. We have found that far-IR magnetic spectra (FIRMS) of Co(PPh 3 ) 2 X 2 (Co-X; X=Cl, Br, I) reveal rarely observed spin-phonon coupling as avoided crossings between magnetic and u-symmetry phonon transitions. Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero-field split (ZFS) levels of the S=3/2 electronic ground state were probed by INS, high-frequency and -field EPR (HFEPR), FIRMS, and frequency-domain FT terahertz EPR (FD-FT THz-EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) and g values. Ligand-field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities in Co-X, showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude. The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin-phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling., (© 2021 Wiley-VCH GmbH.)

Incorporating radical ligands into metal complexes is one of the emerging trends in the design of single-molecule magnets (SMMs). While significant effort has been expended to generate multinuclear transition metal-based SMMs with bridging radical ligands, less attention has been paid to mononuclear transition metal-radical SMMs. Herein, we describe the first α-diiminato radical-containing mononuclear transition metal SMM, namely, [κ 2 -PhTt t Bu ]Fe(AdNCHCHNAd) ( 1 ), and its analogue [κ 2 -PhTt t Bu ]Fe(CyNCHCHNCy) ( 2 ) (PhTt t Bu = phenyltris( tert- butylthiomethyl)borate, Ad = adamantyl, and Cy = cyclohexyl). 1 and 2 feature nearly identical geometric and electronic structures, as shown by X-ray crystallography and electronic absorption spectroscopy. A more detailed description of the electronic structure of 1 was obtained through EPR and Mössbauer spectroscopies, SQUID magnetometry, and DFT, TD-DFT, and CAS calculations. 1 and 2 are best described as high-spin iron(II) complexes with antiferromagnetically coupled α-diiminato radical ligands. A strong magnetic exchange coupling between the iron(II) ion and the ligand radical was confirmed in 1 , with an estimated coupling constant J < -250 cm -1 ( J = -657 cm -1 , DFT). Calibrated CAS calculations revealed that the ground-state Fe(II)-α-diiminato radical configuration has significant ionic contributions, which are weighted specifically toward the Fe(I)-neutral α-diimine species. Experimental data and theoretical calculations also suggest that 1 possesses an easy-axis anisotropy, with an axial zero-field splitting parameter D in the range from -4 to-1 cm -1 . Finally, dynamic magnetic studies show that 1 exhibits slow magnetic relaxation behavior with an energy barrier close to the theoretical maximum, 2| D| . These results demonstrate that incorporating strongly coupled α-diiminato radicals into mononuclear transition metal complexes can be an effective strategy to prepare SMMs.

Introducing both tetrazine radical and azido bridges afforded two air-stable square complexes [M II 4 (bpztz •- ) 4 (N 3 ) 4 ] (M II = Zn 2+ , 1 ; Co 2+ , 2 ; bpztz = 3,6-bis(3,5-dimethylpyrazolyl)-1,2,4,5-tetrazine), where the metal ions are cobridged by μ 1,1 -azido bridges and tetrazine radicals. Magnetic studies revealed strong antiferromagnetic metal-radical interaction with a coupling constant of -64.7 cm -1 in the 2 J formalism in 2 . Remarkably, 2 exhibits slow relaxation of magnetization with an effective barrier for spin reverse of 96 K at zero applied field.

New axially blocked unsymmetrical dirhodium complexes photocatalyze the production of H2 under red light irradiation with a turnover number (TON) of 23 ± 3 in the presence of acid and a sacrificial donor. The presence of multiple metal/ligand-to-ligand charge transfer transitions improves their absorption of light into the near-IR.

An unusual dinuclear rhodium complex with the anionic 2-mercapto-6-methylpyridinate (mmp) bridging ligand is reported which is capable of undergoing significant variations in its structural and coordination environments as a result of two reversible redox events at accessible potentials ( E 1/2 = 0.014, 0.52 V vs Ag/AgCl). The large degree of separation between these redox states (Δ E = 0.51 V, K C = 4.17 × 10 8 ) allows for the chemical isolation of three distinct complexes 1 , 2 , and 3 , in which the oxidation states of each Rh center are Rh 2 I,I , Rh 2 I,II , and Rh 2 II,II , respectively, and whose solid-state structures were elucidated by single crystal X-ray diffraction studies. Complex 2 is an unprecedented type of mixed valence dirhodium species whose electron paramagnetic resonance spectrum revealed a delocalization of the unpaired electron through the thiolate-bridging ligand. Intervalence charge transfer occurs between the Rh centers, as evidenced by a broad absorption in the near-infrared region (λ max = 1187 nm). The structure of 3 is quite rare in that it lacks the typical Rh II -Rh II σ bond, but significant orbital overlap between the Rh 4d z 2 and S 3p z orbitals results in a strong antiferromagnetic coupling (computed J = -1516.9 cm -1 ). Complex 3 also absorbs low-energy light (λ max = 779 nm). Spectroscopic and magnetic measurements are supported by density functional theory methods, which further elucidate the nature of the ground state energies, frontier orbital characters, excited state transitions, and presence of weak Rh-Rh natural bond orbital interactions.

A series of trans -dicyanide vanadium(III) compounds based on acetylacetonate, (PPN)[V III (acac) 2 (CN) 2 ]·(PPN)Cl·2MeCN ( 1 ), and salen ligands, (Et 4 N)[V III (salen)(CN) 2 ] ( 2a ), (PPN)[V III (MeOsalen)(CN) 2 ]·DMF·2MeCN ( 3 ), and (PPN)[V III (salphen)(CN) 2 ]·DMF ( 4 ) [salen = N , N '-ethylenebis(salicyl-imine), MeOsalen = N , N '-ethylenebis(methoxysalicylimine), salphen = N , N '-phenylenebis(salicyl-imine), and PPN = bis(triphenylphosphine)iminium], were prepared and structurally characterized. High-field EPR studies reveal that the complexes exhibit moderate magnetic anisotropy with positive D values of +5.70, +3.80, +4.05, and +3.99 cm -1 for 1 - 4 , respectively.

The combined experimental and theoretical investigation of the magnetic properties of the cobalt(ii) NHC complexes (NHC = N-heterocyclic carbene); [Co(CH2SiMe3)2(IPr)] (1), [CoCl2(IMes)2] (2) and [Co(CH3)2(IMes)2] (3) revealed a large easy plane anisotropy for 1 (D = +73.7 cm-1) and a moderate easy axis anisotropy for 2 (D = -7.7 cm-1) due to significant out-of-state spin-orbit coupling. Dynamic magnetic measurements revealed slow relaxation of the magnetization for 1 (Ueff = 22.5 K, τ0 = 3 × 10-7 s, 1000 Oe) and for 2 (Ueff = 20.2 K, τ0 = 1.73 × 10-8 s, 1500 Oe). The molecular origin of the slow relaxation phenomena was further supported by the retention of AC signal in 10% solutions in 2-MeTHF which reveals a second zero field AC signal in 1 at higher frequencies. Compound 3 was found to be an S = 1/2 system.

A new family of radical-bridged compounds, (Cp*2Co)[M2Cl4(dpq)] (M = Fe (1), Co (2), Zn (3)), (dpq = 2,3-di(2-pyridyl)-quinoxaline) is reported. Magnetic studies, DFT and ab initio calculations reveal strong antiferromagnetic metal-radical interactions with coupling constants of J = -213.1 and -218.8 cm-1 for 1 and 2, respectively.

Electrochemical stability and delocalization of states critically impact the functions and practical applications of electronically active polymers. Incorporation of a ladder-type constitution into these polymers represents a promising strategy to enhance the aforementioned properties from a fundamental structural perspective. A series of ladder-type polyaniline-analogous polymers are designed as models to test this hypothesis and are synthesized through a facile and scalable route. Chemical and electrochemical interconversions between the fully oxidized pernigraniline state and the fully reduced leucoemeraldine state are both achieved in a highly reversible and robust manner. The protonated pernigraniline form of the ladder polymer exhibits unprecedented electrochemical stability under highly acidic and oxidative conditions, enabling the access of a near-infrared light-absorbing material with extended polaron delocalization in the solid-state. An electrochromic device composed of this ladder polymer shows distinct switching between UV- and near-infrared-absorbing states with a remarkable cyclability, meanwhile tolerating a wide operating window of 4 volts. Taken together, these results demonstrate the principle of employing a ladder-type backbone constitution to impart superior electrochemical properties into electronically active polymers., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The geometry of cobalt(ii) ions in the axially distorted octahedral cation in [Co(MeCN)6](BF4)2 (1) was compared to the trigonal prismatic cation in [CoTppy]PF6 (2) which revealed significant differences in magnetic anisotropy. Combined experimental and ab initio CASSCF/NEVPT2 calculations support the observed zero field SMM behaviour for 2, with easy axis anisotropy, attributed to the rigidity of the trigonal prismatic ligand. Strong transverse anisotropy for 1 leads to significant quantum tunnelling processes.

Anisotropic magnetic exchange is of great value for the design of high performance molecular nanomagnets. In the present work, enhanced single-chain magnet (SCM) behavior is observed for a Mo III -Mn II chain that exhibits anisotropic magnetic exchange. Self-assembly of the pentagonal bipyramidal [Mo(CN) 7 ] 4- anion and the Mn II unit with a tridentate ligand results in a neutral double zigzag 2,4-ribbon structure which exhibits SCM behavior with a high relaxation barrier of 178(4) K. Open magnetic hysteresis loops are observed below 5.2 K, with a coercive field of 1.5 T at 2 K. Interestingly, this SCM can be considered to be a result of a step-wise process based on our previously reported Mn 2 Mo single-molecule magnets (SMMs)., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two mononuclear trigonal prismatic Co(II) complexes [Co(tppm*)][BPh 4 ] 2 ( 1 ) and [Co(hpy)][BPh 4 ] 2 ·3CH 2 Cl 2 ( 2 ) (tppm* = 6,6',6″-(methoxymethanetriyl)tris(2-(1 H -pyrazol-1-yl)pyridine; hpy = tris(2,2'-bipyrid-6-yl)methanol) were synthesized by incorporating the Co(II) ions in two pocketing tripodal hexadentate ligands. Magnetic studies indicate similar uniaxial magnetic anisotropy while having distinct dynamic magnetic properties for two complexes, of which 1 exhibits clear hysteresis loops and Orbach process governed magnetic relaxation with an effective energy barrier ( U eff ) of 192 cm -1 , among the best examples in transition metallic SIMs, about 10 times larger than that of 2 ( U eff = 20 cm -1 , extracted by fitting the data to an Orbach relaxation process but there is no real state at this energy). Such pronounced difference is ascribed to the dominant Raman process and quantum tunneling of magnetization (QTM) in 2 owing to the structural distortion and symmetry breaking, indicated by a nearly perfect trigonal prismatic geometry ( D 3 local symmetry) for 1 and a more distorted configuration for 2 ( C 3 local symmetry). Ab initio calculations predict strong axial anisotropy for 1 with minimal QTM probability, with the transverse component of anisotropy being estimated to be much higher for 2 than 1 , leading to a 10-fold lower U eff value than 1 .

Three mononuclear octahedral Co(II) complexes are reported, [Co(py) 4 (SCN) 2 ] ( 1 ), [Co(py) 4 (Cl) 2 ]·H 2 O ( 2 ), and [Co(py) 4 (Br) 2 ] ( 3 ), that exhibit different distortions with compression ( 1 ) or elongation ( 2 and 3 ) of the axial positions. Easy plane magnetic anisotropy was confirmed by magnetic, HF-EPR, and computational studies for all complexes. Further analyses indicate that both the sign and magnitude of zero-field splitting parameters experience a significant change ( D ≥ ±150 cm -1 ) by tuning of the axial and equatorial ligand field strength. Slow magnetic relaxation is observed for all compounds which is dominated by the Raman process involving both acoustic and optical phonons.

Structural, magnetic and theoretical studies of three octahedral mononuclear DyIII complexes with triphenylphosphine oxide and halide ligands are reported. The Cl- and Br- analogues exhibit SMM behavior with energy barriers of 49.1 K and 70.9 K, respectively under a small dc field. Ab initio calculations were performed, the results of which predict higher energy barriers for iodide containing SMMs.

The cis - and trans -dirhodium(II,II) complexes cis -[Rh 2 (μ-DTolF) 2 (μ-np)(MeCN) 4 ][BF 4 ] 2 ( 1 ; DTolF = N , N '-di- p -tolylformamidinate and np = 1,8-naphthyridine), cis - and trans -[Rh 2 (μ-DTolF) 2 (μ-qxnp)(MeCN) 3 ][BF 4 ] 2 [ 2 and 3 , respectively, where qxnp = 2-(1,8-naphthyridin-2-yl)quinoxaline], and trans -[Rh 2 (μ-DTolF) 2 (μ-qxnp) 2 ][BF 4 ] 2 ( 4 ) were synthesized and characterized. A new synthetic methodology was developed that consists of the sequential addition of π-accepting axially blocking ligands to favor formation of the first example of a bis-substituted formamidinate-bearing trans product. Isolation of the intermediates 2 and 3 provides insight into the mechanistic requirements for obtaining 4 and the cis analogue, cis -[Rh 2 (μ-DTolF) 2 (μ-qxnp) 2 ][BF 4 ] 2 ( 5 ). Density functional theory calculations provide support for the synthetic mechanism and proposed intermediates. The metal/ligand-to-ligand charge-transfer (ML-LCT) absorption maximum of the trans complex 4 at 832 nm is red-shifted by 1173 cm -1 and exhibits shorter lifetimes of the 1 ML-LCT and 3 ML-LCT excited states, 3 ps and 0.40 ns, respectively, compared to those of the cis analogue 5 . The shorter excited-state lifetimes of 4 are attributed to the longer Rh-Rh bond of 2.4942(8) Å relative to that in 5 , 2.4498(2) Å. A longer metal-metal bond reflects a decreased overlap of the Rh atoms, which leads to more accessible metal-centered excited states for radiationless deactivation. The 3 ML-LCT excited states of 4 and 5 undergo reversible bimolecular charge transfer with the electron donor p -phenylenediamine when irradiated with low-energy light. These results indicate that trans isomers are a source of unexplored tunability for potential p-type semiconductor applications and, given their distinct geometric arrangement, constitute useful building blocks for supramolecular architectures with potentially interesting photophysical properties.

Polyaniline derivatives represent one of the most widely used classes of conductive polymers. The fundamentally important electronic properties of pernigraniline salts, the fully oxidized and acid-doped derivatives of polyanilines, however, are still not well-understood due to their poor stability and configurational uncertainty. To address these issues and to synthetically access stable analogues of pernigraniline salts, ladder-type constitution was imparted into a series of model oligomer analogues with rigid backbones constituted by up to 27 fused rings. The syntheses were achieved through iterative cross-coupling reactions followed by cyclization and oxidation. In contrast to their unstable non-ladder-type counterparts, these ladder-type pernigraniline-like molecules all adopt a well-defined all- trans configuration and demonstrate an excellent chemical stability after protonation, rendering it possible to reveal the intrinsic electronic and magnetic properties of molecules resembling pernigraniline. Protonated salts of these oligomers feature a significant diradicaloid open-shell resonance contribution. A dominant temperature-independent Pauli paramagnetism was observed in the solid state, an indication of the delocalization nature of the polarons in ladder-type analogues of pernigraniline salt.

Magnetic photoswitching is a highly important but relatively rare phenomenon for enabling optical writing/reading of the magnetic state of a molecule. In this work, an unprecedented site-selective double photoswitching is reported from the assembly of two different "photomagnetic chromophores" into a single hexanuclear molecule: namely, a spin-crossover Fe(II) center exhibiting light-induced excited spin state trapping (LIESST) and a photochemically active octacyanometalate(IV) unit. Four different magnetization levels are accessible through the appropriate combination of violet/red light and temperature, results that highlight the potential of photomagnetic molecules as future molecular memory cells.

Four new three-dimensional (3-D) coordination frameworks based on the heptacyanomolybdate(iii) anion were prepared and characterised by magnetic measurements: {[Mn II (imH) 2 ] 2 [Mn II (H 2 O)(imH) 3 ][Mn II (imH) 4 ] [Mo III (CN) 7 ] 2 ·6H 2 O} n (1) (imH = imidazole), {[Mn II (H 2 O) 2 (imH)] 3 [Mn II (H 2 O)(imH) 2 ][Mo III (CN) 7 ] 2 ·5H 2 O} n (2), {[Mn II (Htrz)(H 2 O) 2 ][Mn II (Htrz) 0.7 (H 2 O) 2.3 ][Mo III (CN) 7 ]·5.6H 2 O} n (3) (Htrz = 1,2,4-triazole) and {[Mn II (H 2 O) 2 ] 3 [Mn II (H 2 O) 4 ][Mo III (CN) 7 ] 2 ·6H 2 O·2urea} n (4). All four compounds exhibit long-range ferrimagnetic ordering and exhibit an opening of their magnetic hysteresis loops at 1.8 K; 1 and 2 exhibit the highest coercive fields among all known [Mo III (CN) 7 ]-based assemblies, 5000 and 4500 Oe respectively. The coercivity of 1-4 is correlated with the geometry of the heptacyanomolybdate(iii) anion and the cyanide bridging pattern. A paramagnetic analogue of compound 1, {[Mn II (imH) 2 ] 2 [Mn II (H 2 O)(imH) 3 ][Mn II (imH) 4 ][Re III (CN) 7 ] 2 ·6H 2 O} n (1Re), where the heptacyanomolybdate(iii) anion is substituted by the diamagnetic heptacyanorhenate(iii) anion is also reported which constitutes the first example of a coordination framework based on [Re III (CN) 7 ] 4- .

Ruthenium compounds with coordinated photolabile molecules that can be selectively released by irradiation with a visible light source are finding increasing applications in photoactivated chemotherapy (PCT) as photocages. Earlier photocages based on mononuclear Ru(II) compounds lack absorption in the therapeutic window (λ > 600 nm). In previous work, we synthesized the first partially solvated tppz bridged (tppz= 2,3,5,6-tetrakis(pyridin-2-yl)pyrazine) dinuclear Ru(II) complex capable of photoinduced ligand exchange at both metal centers. To further explore the effect of the bridging ligand on Ru(II) photocage design, we used quinoxaline-functionalized bridging ligand platforms to prepare [{Ru II (NCCH 3 ) 4 } 2 (μ-BL)](PF 6 ) 4 [BL = dpq, 2,3-di(pyridin-2-yl)quinoxaline ( 1 ); BL = dpb, 2,3-di(pyridin-2-yl)benzo[ g ]quinoxaline ( 2 )]. The compounds are capable of absorbing green light with tails extending beyond 650 nm which can be exploited for applications as PCT agents. Experimental results were additionally verified by DFT calculations. The use of two Ru(II) centers equipped with quinoxaline-based bridging ligands is a promising design strategy for the synthesis of a new family of dinuclear Ru(II) photocage prototypes with the ability to absorb low-energy visible light.

Self-assembly reactions of CoII ions in the presence of the 2,2-bipyrimidine (bpym) ligand produced both a dinuclear and an octanuclear cation with the nuclearity being governed by hydrogen-bonding versus anion-π interactions between the anions and the ligands.

There has been a long-standing discussion in the scientific literature on the thallium (Tl) binding capacity of ferric hexacyanoferrate (insoluble) and potassium hexacyanoferrate (soluble) forms of Prussian blue (PB). The literature sometime suggests that the soluble form of PB should be used to treat thallium poisoning, instead of the FDA approved insoluble form of PB. The literature debate is further complicated by the lack of fundamental characterization data such as critical quality attributes (CQAs) that clearly define the analog forms. The purpose of this study is to compare, the binding capacity of soluble and insoluble PB analogs with the same CQAs (particle size/distribution and water content). Water content and particle size/particle distribution were determined by TGA, and solid-state laser diffraction particle sizing. Thallium binding studies were conducted at physiological pH to determine the maximal binding capacity (MBC) at equilibrium. Multiple linear regression and principal component analysis was also used for multivariate data analysis. Results indicate that insoluble and soluble analogs, with similar quality attributes, have nearly identical, MBC binding capacities of (441.5 mg/g) for insoluble vs soluble (458.4 mg/g). However, when both analog forms with different CQAs such as water, particle size were compared, results indicated significantly higher or lower thallium binding levels. In conclusion, it is essential that the FDA approved iron form with well-defined CQAs is used to treat thallium poisoning and radioactive thallium metal contamination for consistent therapeutic outcomes., (Published by Elsevier B.V.)

Two new homoleptic DyIII compounds [Dy(TpMe2)2][DyCl3(TpMe2)]·CH2Cl2 (1) and [Dy(TpMe2)2]I (3) as well as a heteroleptic (NMe4)[DyCl3(TpMe2)] (2) (TpMe2 = tris(3,5-dimethylpyrazolyl)borate) species are reported. Magnetic studies revealed that 1 is a single-molecule magnet (SMM) with an energy barrier of Ueff = 80.7 K with τ0 = 6.2 × 10-7 s under a zero applied field. Compound 3 exhibits a Ueff of 13.5 K with τ0 = 1.6 × 10-6 s under a 0.08 T applied field. Ab initio CASSCF + RASSI-SO calculations were performed to further investigate the magnetic behavior of complexes 1-3. The results support experimental magnetic data for 1 and 3 and indicate that an intermolecular dipolar interaction of (zJ = -0.1 cm-1) is responsible for the SMM behavior of 1.

Three mononuclear metal complexes [MII(L-N3O2)(MeCN)2][BPh4]2 (M = Fe, 1; Co, 2; Ni, 3) were isolated and structurally characterized. Magnetic studies revealed uniaxial magnetic anisotropy for 1 (D = -17.1 cm-1) and 3 (D = -14.3 cm-1) and easy-plane magnetic anisotropy for 2 (D = +36.9 cm-1). Slow magnetic relaxation was observed for complexes 1 and 2 under an applied magnetic field, both of which are dominated by a Raman process.

Two dinuclear lanthanide complexes (Gd and Dy) were prepared and characterized by X-ray, magnetic and computational methods. The Dy analogue shows SMM behavior with an energy barrier of 98.4 K in the absence of an applied dc field. Theoretical calculations were performed on model complexes which support the hypothesis that the energy barrier will increase if the soft-donor atoms S and Se are used in lieu of an O donor.

Practical applications involving the magnetic bistability of single-molecule magnets (SMMs) for next-generation computer technologies require nanostructuring, organization, and protection of nanoscale materials in two- or three-dimensional networks, to enable read-and-write processes. Owing to their porous nature and structural long-range order, metal-organic frameworks (MOFs) have been proposed as hosts to facilitate these efforts. Although probing the channels of MOF composites using indirect methods is well established, the use of direct methods to elucidate fundamental structural information is still lacking. Herein we report the direct imaging of SMMs encapsulated in a mesoporous MOF matrix using high-resolution transmission electron microscopy. These images deliver, for the first time, direct and unambiguous evidence to support the adsorption of molecular guests within the porous host. Bulk magnetic measurements further support the successful nanostructuring of SMMs. The preparation of the first magnetic composite thin films of this kind furthers the development of molecular spintronics.

Single-molecule magnets (SMMs), are regarded as excellent nanomaterials for high-density information storage and quantum computing. The local symmetry of the crystal field for the metal ion plays an important role in pursuing a high-performance SMM. Herein, two highly stable distorted hexagonal bipyramidal (quasi- D 6 h ) Dy complexes exhibiting slow relaxation of the magnetization are reported. A hexagonal bipyramidal Dy model complex with 18-crown-6 was also designed to study the relationship between magnetic anisotropy and symmetry. The combined experimental and theoretical results indicate that quantum tunneling is highly dependent on the local symmetries of the crystal field. The magnetic anisotropy becomes much stronger when the symmetry is closer to a standard D 6 h geometry. These results support the conclusion that the hexagonal bipyramidal geometry is a viable one for the design of new classes of SMMs.

A new cyclic molecule incorporating [MoIII(CN)7]4- has been characterized by single crystal X-ray methods, SQUID magnetometry and theoretical calculations. The wheel molecule [MoIII(CN)7]6[Ni(L)]12(H2O)6 exhibits ferromagnetic Mo-Ni coupling which did not exist for the previously reported octacyanometallate analogue [MoIV(CN)8]6[Ni(L)]12(H2O)6. These results indicate that known supramolecular architectures incorporating octacyanometallates can be used as platforms for making new molecules incorporating seven-coordinate cyanide precursors.

A rare disk-like single-molecule magnet (SMM) exclusively bridged by end-on azides with a spin ground state of S = 14 was prepared by the reaction of a divalent Fe II precursor with Me 3 SiN 3 under basic conditions. AC magnetic susceptibility studies revealed unusual, "Janus"-faced SMM behavior for the dried and pristine forms of the compound attributed to solvation/de-solvation effects of the coordinated MeCN ligands which leads to alterations in the crystal field and symmetry of the metal ions. DFT calculations confirmed the ferromagnetic nature of the interactions between the Fe II spin carriers with the zero-field splitting parameters D = -0.2323 cm -1 and E / D = 0.027. The results have important implications for the future study of single-molecule magnets incorporating volatile solvent molecules in the first coordination sphere of the metal ions and their effect on the relaxation dynamics.

Human infection by Mycobacterium tuberculosis (Mtb) continues to be a global epidemic. Computer-aided drug design (CADD) methods are used to accelerate traditional drug discovery efforts. One noncovalent interaction that is being increasingly identified in biological systems but is neglected in CADD is the anion-π interaction. The study reported herein supports the conclusion that anion-π interactions play a central role in directing the binding of phenyl-diketo acid (PDKA) inhibitors to malate synthase (GlcB), an enzyme required for Mycobacterium tuberculosis virulence. Using density functional theory methods (M06-2X/6-31+G(d)), a GlcB active site template was developed for a predictive model through a comparative analysis of PDKA-bound GlcB crystal structures. The active site model includes the PDKA molecule and the protein determinants of the electrostatic, hydrogen-bonding, and anion-π interactions involved in binding. The predictive model accurately determines the Asp 633-PDKA structural position upon binding and precisely predicts the relative binding enthalpies of a series of 2-ortho halide-PDKAs to GlcB. A screening model was also developed to efficiently assess the propensity of each PDKA analog to participate in an anion-π interaction; this method is in good agreement with both the predictive model and the experimental binding enthalpies for the 2-ortho halide-PDKAs. With the screening and predictive models in hand, we have developed an efficient method for computationally screening and evaluating the binding enthalpy of variously substituted PDKA molecules. This study serves to illustrate the contribution of this overlooked interaction to binding affinity and demonstrates the importance of integrating anion-π interactions into structure-based CADD.

Ru(II)-polypyridyl complexes exhibit antitumor properties that can be systematically tailored by means of adjusting the ligand environment. In this work, the effect of incorporating π-extended moieties into anionic N ∧ O - based chelating ligands on the cytotoxic properties of Ru compounds is explored. Four new Ru(II) complexes, [Ru(bpy) 2 (dphol)][PF 6 ] (1; bpy = 2,2'-bipyridine, dphol = dibenzo[ a, c]phenazin-10-olate), [Ru(phen) 2 (dphol)][PF 6 ] (2; phen = 1,10-phenanthroline), [Ru(bpy) 2 (hbtz)][PF 6 ] (3; hbtz = 2-(benzo[ d]thiazol-2-yl)phenolate), and [Ru(phen) 2 (hbtz)][PF 6 ] (4) were synthesized and thoroughly characterized. In vitro cytotoxicity was investigated in human lung adenocarcinoma (A549) cells, which revealed that 4 is the most cytotoxic compound (IC 50 = 0.8 μM) in the series including a control compound [Ru(bpy) 2 (quo)][PF 6 ] (5; quo = 8-hydroxyquinolinate) and is nearly 8-fold more cytotoxic than cisplatin. An investigation of the mechanism of cell death led to the finding that compounds 1-4 disrupt the mitochondrial transmembrane potential (ΔΨ m ) in a concentration-dependent fashion, which is an event associated with the intrinsic pathway of apoptosis. Moreover, compound 4 triggers the activity of caspase-3/7, which eventually induces the apoptotic cellular death of A549 cells. Thus, increasing the overall lipophilicity of the Ru compounds by introducing π-extended moieties in the anionic N ∧ O - ligand is a successful strategy for realizing a new family of pro-apoptotic compounds with a [Ru II N 5 O] + coordination environment.

Geometric control in mononuclear complexes has come to the forefront in the field of molecular magnets due to its profound effects on relaxation pathways and blocking temperature in single molecule magnets (SMMs). Herein we report the synthesis and magnetic characterization of six trigonally symmetric, divalent Fe, Co, and Ni molecules, with the rigid geometry enforced via the use of the tris-anionic, tetradentate ligand MST ( N , N ', N ''-[2,2',2''-nitrilotris-(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamide)). A systematic study on the effect of converting between trigonal monopyramidal complexes, (Me 4 N)[M(MST)], and trigonal bipyramidal complexes, (Me 4 N)[M(MST)(OH 2 )] was conducted experimentally and computationally. It was found that (Me 4 N)[Ni(MST)] exhibits a very large, near record zero-field splitting parameter ( D ) value of -434 cm -1 , owing to an extremely low lying first excited state. The trigonal monopyramidal cobalt and iron complexes exhibit slow magnetic relaxation under applied fields, resulting in barriers of 45 K and 63.9 K respectively. Coordination of a single water molecule in the open axial site of the trigonal monopyramidal complexes exerts drastic dampening effects on the D value as well as slow relaxation. Computations reveal that coordination of water rotates the D zz axis away from the C 3 axis of symmetry resulting in a smaller D value. The aquo species (Me 4 N)[Co(MST)(OH 2 )] also exhibits magnetic relaxation under an applied field, but the barrier is reduced to 9.9 K. Water coordination totally quenches the magnetic behavior in the iron complex, and reduces the D value for nickel to -185 cm -1 . These results showcase the drastic effect that a small change in the coordination environment can have on magnetic behavior, as well as that trigonal monopyramidal geometry can lead to near record D values.

A new family of mononuclear lanthanide complexes, where the eight coordinate lanthanide ions adopt a very rare cubic coordination geometry is reported. The Dy analogue exhibits SMM behavior with a Ueff value 95.7 K under a 0.02 T applied dc field. Ab initio calculations support the observed magnetic behavior.

Photocatalytic proton reduction to generate H2 was achieved with the photosensitizers Rh2(DTolF)2(npCOO)2 (DTolF = p-ditolylformamidinate; npCOO- = 2-carboxylate-1,8-naphthyridine; 1) and [Rh2(DTolF)2(qnnp)2][BF4]2 (qnnp = 2-(quinolin-2-yl)-1,8-naphthyridine; 2) using a relay system containing the sacrificial donor BNAH (1-benzyl-1,4-dihydronicotinamide), electron acceptor MV2+ (methylviologen), and Pt nanoparticles as the catalyst with 655 nm irradiation. Comparison of the H2 evolution under similar experimental conditions show comparable activity of the Rh2(ii,ii) complexes (λirr = 655 nm) to that of the prototypical [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine; 3) with λirr = 447 nm. This work demonstrates the ability of the new panchromatic Rh2(ii,ii) complexes to achieve photocatalysis with red light.

A series of dirhodium(II,II) paddlewheeel complexes of the type cis-[Rh 2 (μ-DTolF) 2 (μ-L) 2 ][BF 4 ] 2 , where DTolF = N,N'-di( p-tolyl)formamidinate and L = 1,8-naphthyridine (np), 2-(pyridin-2-yl)-1,8-naphthyridine (pynp), 2-(quinolin-2-yl)-1,8-naphthyridine (qnnp), and 2-(1,8-naphthyridin-2-yl)quinoxaline (qxnp), were synthesized and characterized. These molecules feature new tridentate ligands that concomitantly bridge the dirhodium core and cap the axial positions. The complexes absorb light strongly throughout the ultraviolet/visible range and into the near-infrared region and exhibit relatively long-lived triplet excited-state lifetimes. Both the singlet and triplet excited states exhibit metal/ligand-to-ligand charge transfer (ML-LCT) in nature as determined by transient absorption spectroscopy and spectroelectrochemistry measurements. When irradiated with low-energy light, these black dyes are capable of undergoing reversible bimolecular electron transfer both to the electron acceptor methyl viologen and from the electron donor p-phenylenediamine. Photoinduced charge transfer in the latter was inaccessible with previous Rh 2 (II,II) complexes. These results underscore the fact that the excited state of this class of molecules can be readily tuned for electron-transfer reactions upon simple synthetic modification and highlight their potential as excellent candidates for p- and n-type semiconductor applications and for improved harvesting of low-energy light to drive useful photochemical reactions.

The first examples of metallacycles containing rare earth ions bridged by radicals are reported. The molecular triangles [Ln 3 (hfac) 6 (bptz •- ) 3 ] (Ln = Dy III , Y III ; hfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine) consist of lanthanide ions bridged by bptz radical anion (bptz •- ) ligands. Magnetic susceptibility measurements and CASSCF calculations performed on [Dy 3 (hfac) 6 (bptz •- ) 3 ] reveal the presence of antiferromagnetic coupling between the Dy III centers and the bptz •- ligands, with J = -6.62 cm -1 .

A new octacyanotungstate(v) based single chain magnet {[(Tpm)Co(DMF)W(CN) 8 ] 2 [Co(DMF) 4 ]·2DMF} n ( 1 , Tpm = 1,1,1-trispyrazoylmethane), with an effective barrier of 39.7(3) cm -1 is reported. The Ising-like magnetic anisotropy of the chain originates from the nearly parallel local orientations of the Co(ii) ions with the source of the uniaxial magnetic anisotropy being a trigonal distortion of the octahedral environment with the fac -tridentate capping Tpm ligand.

The radical bridged compound [(Ni(TPMA)) 2 -μ-bmtz •- ](BF 4 ) 3 ·3CH 3 CN (bmtz = 3,6-bis(2'-pyrimidyl)-1,2,4,5-tetrazine, TPMA = tris(2-pyridylmethyl)amine) exhibits strong ferromagnetic exchange between the S = 1 Ni II centers and the bridging S = 1/2 bmtz radical with J = 96 ± 5 cm -1 (-2J Ni-rad S Ni S rad ). DFT calculations support the existence of strong ferromagnetic exchange.

The iron(II) semiquinonate character within the iron(III) catecholate species has been proposed by numerous studies to account for the O 2 reactivity of intradiol catechol dioxygenases, but a well-characterized iron(II) semiquinonate species that exhibits intradiol cleaving reactivity has not yet been reported. In this study, a detailed electronic structure description of the first iron(II) o-semiquinonate complex, [PhTt tBu ]Fe(phenSQ) [PhTt tBu = phenyltris(tert-butylthiomethyl)borate; phenSQ = 9,10-phenanthrenesemiquinonate; Wang et al. Chem. Commun. 2014, 50, 5871-5873], was generated through a combination of electronic and Mössbauer spectroscopies, SQUID magnetometry, and density functional theory (DFT) calculations. [PhTt tBu ]Fe(phenSQ) reacts with O 2 to generate an intradiol cleavage product, diphenic anhydride, in 16% yield. To assess the dependence of the intradiol reactivity on the identity of the metal ion, the nickel analogue, [PhTt tBu ]Ni(phenSQ), and its derivative, [PhTt tBu ]Ni(3,5-DBSQ) (3,5-DBSQ = 3,5-di-tert-butyl-1,2-semiquinonate), were prepared and characterized by X-ray crystallography, mass spectrometry, 1 H NMR and electronic spectroscopies, and SQUID magnetometry. DFT calculations, evaluated on the basis of the experimental data, support the electronic structure descriptions of [PhTt tBu ]Ni(phenSQ) and [PhTt tBu ]Ni(3,5-DBSQ) as high-spin nickel(II) complexes with antiferromagnetically coupled semiquinonate ligands. Unlike its iron counterpart, [PhTt tBu ]Ni(phenSQ) decomposes slowly in an O 2 atmosphere to generate 14% phenanthrenequinone with a negligible amount of diphenic anhydride. [PhTt tBu ]Ni(3,5-DBSQ) does not react with O 2 . This dramatic effect of the metal-ion identity supports the hypothesis that a metal(III) alkylperoxo species serves as an intermediate in the intradiol cleaving reactions. The redox properties of all three complexes were probed using cyclic voltammetry and differential pulse voltammetry, which indicate an inner-sphere electron-transfer mechanism for the formation of phenanthrenequinone. The lack of O 2 reactivity of [PhTt tBu ]Ni(3,5-DBSQ) can be rationalized by the high redox potential of the metal-ligated 3,5-DBSQ/3,5-DBQ couple.

Dynamic molecular crystals are of high interest due to their potential applications. Herein we report the reversible on-off switching of single-molecule magnet (SMM) behavior in a [Mo(CN) 7 ] 4- based molecular compound. Upon dehydration and rehydration, the trinuclear Mn 2 Mo molecule [Mn(L)(H 2 O)] 2 [Mo(CN) 7 ]·2H 2 O (1) undergoes reversible crystal-to-crystal transformation to a hexanuclear Mn 4 Mo 2 compound [Mn(L)(H 2 O)] 2 [Mn(L)] 2 [Mo(CN) 7 ] 2 (2). This structural transformation involves the breaking and reforming of coordination bonds which leads to significant changes in the color and magnetic properties. Compound 1 is an SMM with an energy barrier of 44.9 cm -1 , whereas 2 behaves as a simple paramagnet despite its higher ground state spin value. The distortion of the pentagonal bipyramidal geometry of [Mo(CN) 7 ] 4- in 2 disrupts the anisotropic exchange interactions that lead to SMM behavior in 1.

The synthesis of two new radical-bridged compounds [Co 3 (bptz) 3 (dbm) 3 ]·2toluene (1) and [Co 4 (bptz) 4 (dbm) 4 ]·4MeCN (2) (bptz = 3,6-bis(pyridyl)-1,2,4,5-tetrazine; dbm = 1,3-diphenyl-1,3-propanedionate) is reported. The presence of the ligand-centered radical has been confirmed by X-ray crystallography and SQUID magnetometry. These complexes are the first metallacycles bearing nitrogen heterocyclic radicals as bridges. Magnetic studies reveal strong antiferromagnetic metal···radical coupling with coupling constants of J = -67.5 and -66.8 cm -1 for 1 and 2, respectively. DFT calculations further support the strong antiferromagnetic coupling between Co II ions and bptz radicals and confirm S = 3 and S = 4 spin ground states for 1 and 2, respectively.

This is the first systematic study exploring metal-organic frameworks (MOFs) as platforms for the controlled nanostructuring of molecular magnets. We report the incorporation of seven single-molecule magnets (SMMs) of general composition [Mn 12 O 12 (O 2 CR) 16 (OH 2 ) 4 ], with R = CF 3 (1), (CH 3 )CCH 2 (2), CH 2 Cl (3), CH 2 Br (4), CHCl 2 (5), CH 2 Bu t (6), and C 6 H 5 (7), into the hexagonal channel pores of a mesoporous MOF host. The resulting nanostructured composites combine the key SMM properties with the functional properties of the MOF. Synchrotron-based powder diffraction with difference envelope density analysis, physisorption analysis (surface area and pore size distribution), and thermal analyses reveal that the well-ordered hexagonal structure of the host framework is preserved, and magnetic measurements indicate that slow relaxation of the magnetization, characteristic of the corresponding Mn 12 derivative guests, occurs inside the MOF pores. Structural host-guest correlations including the bulkiness and polarity of peripheral SMM ligands are discussed as fundamental parameters influencing the global SMM@MOF loading capacities. These results demonstrate that employing MOFs as platforms for the nanostructuration of SMMs is not limited to a particular host-guest system but potentially applicable to a multitude of other molecular magnets. Such fundamental findings will assist in paving the way for the development of novel advanced spintronic devices.

Two cyanide-bridged compounds based on the Fe II cation and the anisotropic [Mo III (CN) 7 ] 4- anion, namely, {Fe 2 (H 2 O) 5 [Mo(CN) 7 ]·5H 2 O} n (1) and {[NH 2 (CH 3 ) 2 ] 2 Fe 5 (H 2 O) 10 [Mo(CN) 7 ] 3 ·8H 2 O} n (2), have been prepared. Single crystal X-ray analyses revealed that their structures exhibit different three-dimensional topologies as a result of the addition of [NH 2 (CH 3 ) 2 ] + during the synthesis of 2. For both 1 and 2, the geometry of the [Mo(CN) 7 ] 4- unit is a slightly distorted capped trigonal prism; all Fe II centers are hexacoordinate and adopt a distorted octahedral configuration. Compound 1 is a three-nodal 3,4,7-connected net with the point symbol of {4.6 2 }{4 5 .6}{4 6 .6 12 .8 3 }, while compound 2 is a five-nodal 4,4,4,6,7-connected net with the point symbol of {4 4 .6 2 }{4 5 .6} 4 {4 6 .6 7 .8 2 }{4 9 .6 11 .8} 2 . Magnetic studies revealed that both compounds exhibit magnetic ordering below 65 K. Apart from the plethora of Mn II -[Mo(CN) 7 ] 4- compounds documented in the literature, these two Fe II -[Mo(CN) 7 ] 4- compounds are the only other [Mo(CN) 7 ] 4- extended structures to be characterized by single crystal structures to date.

Bifunctional electrically conducting single-molecule magnets are highly promising platforms for non-volatile memory devices and quantum computing applications. The development of these molecular materials, however, has largely been hindered by the lack of straightforward synthetic methods. Herein a facile and modular approach is demonstrated for the realization of bifunctional materials that does not require electrochemical or chemical oxidation to obtain partially charged organic radicals. Magnetic and electrical conductivity studies reveal that the Dy III compound exhibits slow relaxation of the magnetization between 5.0-8.0 K and semiconducting behavior over the range 180-350 K. DC magnetic fields have been found to suppress the quantum tunneling of the magnetization and affect the spin-canted antiferromagnetic interactions., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A building block approach has been used to prepare a new family of hexanuclear magnetic molecules Mn 4 Nb 2 , Fe 4 Nb 2 , and Co 4 Nb 2 of general formula {[M II (tmphen) 2 ] 4 [Nb IV (CN) 8 ] 2 }·solv (M = Mn, Fe, Co; tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline; solv = MeOH and/or H 2 O). Mn 4 Nb 2 exhibits a magnetocaloric effect at temperatures close to 1.8 K, and Fe 4 Nb 2 undergoes an incomplete gradual spin crossover and a photomagnetic response related to light-induced excited spin state trapping.

A family of distorted trigonal pyramidal transition-metal complexes [M II (N 3 N)Li(THF)] (M=Mn, Fe, Co, Ni) have been studied as candidates for mononuclear single-molecule magnets. Magnetic anisotropy of the family depends on the electronic configuration of the central ion, with the Co analogue exhibiting pronounced SMM behavior., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)