Search

To further the ability to manipulate the properties of open-shell molecules, logical and incremental modifications to molecular structure are key steps that provide fine-tuning of established diradicaloid scaffolds. We report the synthesis of an electronically "pure" diradicaloid based on a 2,6-anthroquinoidal core where the once necessary ethynyl "wings" are removed. Through the simplification of the overall electronic structure, the singlet-triplet energy gap increases by 0.3-0.4 kcal mol -1 in the reported diradicaloids while avoiding significant disruption to their optoelectronic properties.

Conductive metal-organic frameworks are of current interest in chemical science because of their applications in chemiresistive sensing, electrochemical energy storage, electrocatalysis, etc. Different strategies have been employed to design conductive frameworks. In this review, we discuss the influence of different types of guest species incorporated within the pores or channels of metal-organic frameworks (MOFs) and porous coordination polymers (PCPs) to generate charge transfer pathways and modulate their electrical conductivity. We have classified dopants or guest species into three different categories: (i) metal-based dopants, (ii) molecule and molecular entities and (iii) organic conducting polymers. Different types of metal ions, metal nano-clusters and metal oxides have been used to enhance electrical conductivity in MOFs. Metal ions and metal nano-clusters depend on the hopping process for efficient charge transfer whereas metal-oxides show charge transport through the metal-oxygen pathway. Several types of molecules or molecular entities ranging from neutral TCNQ, I 2 , and fullerene to ionic methyl viologen, organometallic like nickelcarborane, etc. have been used. In these cases, the charge transfer process varies with the guest species. When organic conducting polymers are the guest, the charge transport occurs through the polymer chains, mostly based on extended π-conjugation. Here we provide a comprehensive and critical review of these strategies to add electrical conductivity to the, in most cases, otherwise insulating MOFs and PCPs. We point out the guest encapsulation process, the geometry and structure of the resulting host-guest complex, the host-guest interactions and the charge transport mechanism for each case. We also present the methods for thin film fabrication of conducting MOFs (both, liquid-phase and gas-phase based methods) and their most relevant applications like electrocatalysis, sensing, charge storage, photoconductivity, photocatalysis,… We end this review with the main obstacles and challenges to be faced and the appealing perspectives of these 21 st century materials.

Three cyano-coordinated cobalt porphyrin dimers were synthesized and thoroughly characterized. The X-ray structure of the complexes reveals that cyanide binds in a terminal fashion in both the anti and trans isomers of ethane- and ethylene-bridged cobalt porphyrin dimers, while in the cis ethylene-bridged dimer, cyanides bind in both terminal and bridging modes. The nonconjugated ethane-bridged complex stabilizes exclusively a diamagnetic metal-centered oxidation of type Co III (por)(CN) 2 both in the solid and in solution. In contrast, the complexes with the conjugated ethylene-bridge contain signatures of both paramagnetic ligand-centered oxidation of the type Co II (por •+ )(CN) 2 and diamagnetic metal-centered oxidation of type Co III (por)(CN) 2 with the metal-centered oxidized species being the major component in the solid state as observed in XPS, while the ligand-centered oxidized species are present in a significant amount in solution. 1 H NMR spectrum in solution displays two set of signals corresponding to the simultaneous presence of both the diamagnetic and paramagnetic species. EPR and magnetic investigation reveal that there is a moderate ferromagnetic coupling between the unpaired electrons of the low-spin Co II center and the porphyrin π-cation radical in Co II (por •+ )(CN) 2 species as well as an antiferromagnetic coupling between the two Co II (por •+ ) units through the ethylene and CN bridges.

A new Mannich base (2-(4-(2-hydroxy-3-methoxy-5-methylbenzyl)-piperazin-1-yl)methyl)-6-methoxy-4-ethylphenol (H2L) and its tetranuclear Ni II complex [Ni 4 L 2 (μ 1,1 -Cl) 2 (H 2 O) 4 ]Cl 2 (compound 1) are characterised using single-crystal X-ray diffraction measurements. Compound 1 contains four different Ni II centres in a rhombus-like structure. Two Ni atoms (Ni1 and Ni2) have a NiN 2 O 4 coordination sphere, while the other two (Ni3 and Ni4) have a NiO 4 Cl 2 coordination environment and Ni-Cl-Ni bridges connect them. Ni1 and Ni2 are linked to Ni3 and Ni4 by phenoxide bridges. Variable temperature magnetic susceptibility measurements of 1 indicate the presence of alternating antiferromagnetic coupling ( J 1 = -6.6(1) cm -1 ) through the phenoxide bridge along the sides of the rhombus and ferromagnetic coupling ( J 2 = 8.4(1) cm -1 ) through the double Cl bridge along the short diagonal of the rhombus with a zero-field splitting of | D | = 2.7(1) cm -1 . Compound 1 shows oxidase (catecholase-like and phenoxazinone synthase-like) activity. The oxidation of 3,5-di- tert -butylcatechol (3,5-DTBC) gives 3,5-di- tert -butylquinone (3,5-DTBQ) and H 2 O 2 and the oxidation of o -aminophenol (OAP) produces 2-aminophenoxazin-3-one (APX) and H 2 O with turnover numbers of 28.32 and 17.52 h -1 , respectively, under aerobic conditions. A mechanism for the oxidase activity catalysed by compound 1 is proposed in line with ESI-mass spectrometry, EPR spectroscopy, and electrochemical data. The reaction involves the cleavage of the tetranuclear Ni 4 -core to form a mononuclear Ni II complex in the presence of the substrate (3,5-DTBC/OAP). This Ni II complex is reduced to Ni I with the concomitant oxidation of the substrate (3,5-DTBQ/APX). Formation of a radical intermediate is confirmed using EPR. In the catecholase-like activity, O 2 is reduced to H 2 O 2 while in the phenoxazinone synthase-like activity O 2 produces H 2 O. Compound 1 participated in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in a strongly basic medium with an onset potential of 418 mV and a Tafel slope of 121 mV dec -1 for OER and an onset potential of 477 mV and Tafel slope of 146 mV dec -1 for HER.

Two families of difluorenoheterole diradicaloids were synthesized, featuring isomeric ring systems with distinct conjugation topologies. The two types of difluorenoheteroles contain, respectively, a Chichibabin-like motif (CH) and a newly introduced heteroatom-linked triphenylmethyl dyad (TD-X). Combined experimental and theoretical investigations show that the TD-X systems have reduced quinoidal character but the interaction between formal spin centers is sufficiently strong to ensure a singlet ground state. The singlet-triplet energy gaps in the TD-X difluorenoheteroles are strongly affected by the heterocyclic ring, with values of -4.3 and -0.7 kcal mol -1 determined for the pyrrole- and thiophene-containing analogues, respectively. In cyclic voltammetry experiments, the TD-X systems show diminished energy gaps and superior reversibility in comparison with their CH counterparts. The radical anions and cations obtained from these diradicaloids show extremely red-shifted bands, occasionally with λ max > 3500 nm. Computational studies show that some of these ions adopt distonic structures and may be characterized as class-II mixed-valence species., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We have prepared and characterized three coordination polymers formulated as [Dy 2 (C 6 O 4 Cl 2 ) 3 (fma) 6 ] ⋅ 4.5fma (1) and [Dy 2 (C 6 O 4 X 2 ) 3 (fma) 6 ] ⋅ 4fma ⋅ 2H 2 O with X=Br (2) and Cl (3), where fma=formamide and C 6 O 4 X 2 2- =3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion with X=Cl (chloranilato) and Br (bromanilato). Compounds 1 and 3 are solvates obtained with slow and fast precipitation methods, respectively. Compounds 2 and 3 are isostructural and only differ in the X group of the anilato ligand. The three compounds present (6,3)-gon two-dimensional hexagonal honey-comb structures. Magnetic measurements indicate that the three compounds show slow relaxation of the magnetization at low temperatures when a continuous magnetic field is applied, although with different relaxation times and energy barriers depending on X and the crystallisation molecules. Compounds 1-3 represent the first examples of anilato-based lattices with formamide and field-induced slow relaxation of the magnetization., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Here we present the magnetic properties of two cobalt complexes formulated as: [Co(SCN) 2 (L) 2 ] (1) and (H 2 L) 2 [Co(SCN) 4 ]·H 2 O (2) (L = 1-(2-pyrimidyl)piperazine). The two compounds contain isolated tetrahedral Co II complexes with important intermolecular interactions that lead to the presence of a canted antiferromagnetic order below 11.5 and 10.0 K, with coercive fields at 2 K of 38 and 68 mT, respectively. Theoretical calculations have been used to explain this behaviour. Hirshfeld surface analysis shows the presence of strong intermolecular interactions in both compounds. The crystal geometries were used for geometry optimization using the DFT method. From the topological properties, electrostatic potential maps and molecular orbital analysis, information about the noncovalent interaction and chemical reactivity was obtained., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We present a bifunctional heptanuclear cobalt(II)/cobalt(III) molecular complex formulated as [Co 7 (μ 3 -OH) 4 (H 2 L 1 ) 2 (HL 2 ) 2 ](NO 3 ) 6 ·6H 2 O ( 1 ) (where H 5 L 1 is 2,2'-(((1E,1'E)-((2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene))bis(azanylylidene))bis(propane-1,3-diol)) and H 2 L 2 is 2-amino-1,3-propanediol). Compound 1 has been characterized by single-crystal X-ray diffraction analysis along with other spectral and magnetic measurements. Structural analysis indicates that 1 contains a mixed-valence Co 7 cluster where a central Co(II) ion is connected to six different Co centers (four Co III and two Co II ions) by four μ 3 -OH groups, giving rise to a planar heptanuclear cluster that resembles a molecular fragment of a layered double hydroxide (LDH). Two triply deprotonated (H 2 L 1 ) 3- ligands form the outer side of the cluster while two singly deprotonated (HL 2 ) - ligands are located at the top and bottom of the central heptanuclear core. Variable temperature magnetic measurements indicate the presence of weak ferromagnetic Co II ···Co II interactions ( J = 3.53(6) cm -1 ) within the linear trinuclear Co II cluster. AC susceptibility measurements show that 1 is a field-induced single-molecule magnet (SMM) with τ 0 = 8.2(7) × 10 -7 s and U eff = 11.3(4) K. The electrocatalytic hydrogen evolution reaction (HER) activity of 1 in homogeneous phase shows an overpotential of 455 mV, with a Faradaic efficiency of 81% and a TOF of 8.97 × 10 4 μmol H 2 h -1 mol -1 .

Heteroatom doping and phase engineering are effective ways to promote the catalytic activity of nanoenzymes. Nitrogen-doped 1 T/2H mixed phase MoS 2 /CuS heterostructure nanosheets N-1 T/2H-MoS 2 /CuS are prepared by a simple hydrothermal approach using polyoxometalate (POM)-based metal-organic frameworks (MOFs) (NENU-5) as a precursor and urea as nitrogen doping reagent. The XPS spectroscopy (XPS) and Raman spectrum of N-1 T/2H-MoS 2 /CuS prove the successful N-doping. NENU-5 was used as the template to prepare 1 T/2H-MoS 2 /CuS with high content of 1 T phase by optimizing the reaction time. The use of urea as nitrogen dopant added to 1 T/2H-MoS 2 /CuS, resulted in N-1 T/2H-MoS 2 /CuS with an increase in the content of the 1 T phase from 80 % to 84 % and higher number of defects. N-1 T/2H-MoS 2 /CuS shows higher peroxidase activity than 1 T/2H-MoS 2 /CuS and a catalytic efficiency (K cat /K m ) for H 2 O 2 twice as high as that of 1 T/2H-MoS 2 /CuS. The enhanced catalytic activity has probably been attributed to several reasons: (i) the insertion of urea during the hydrothermal process in the S-Mo-S layer of MoS 2 , causing an increase in the interlayer spacing and in 1 T phase content, (ii) the replacement of S atoms in MoS 2 by N atoms from the urea decomposition, resulting in more defects and more active sites. As far as we know, N-1 T/2H-MoS 2 /CuS nanosheets have the lowest detection limit (0.16 µm) for the colorimetric detection of hydroquinone among molybdenum disulfide-based catalysts. This study affords a new approach for the fabrication of high-performance nanoenzyme catalysts., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

A series of two-electron-oxidized cobalt porphyrin dimers have been synthesized upon controlled oxidations using halogens. Rather unexpectedly, X-ray structures of two of these complexes contain two structurally different low-spin molecules in the same asymmetric unit of their unit cells: one is the metal-centered oxidized diamagnetic entity of the type Co III (por), while the other one is the ligand-centered oxidized paramagnetic entity of the type Co II (por •+ ). Spectroscopic, magnetic, and DFT investigations confirmed the coexistence of the two very different electronic structures both in the solid and solution phases and also revealed a ferromagnetic spin coupling between Co(II) and porphyrin π-cation radicals and a weak antiferromagnetic coupling between the π-cation radicals of two macrocycles via the bridge in the paramagnetic complex.

Metal-organic frameworks (MOFs), formed by the combination of both inorganic and organic components, have attracted special attention for their tunable porous structures, chemical and functional diversities, and enormous applications in gas storage, catalysis, sensing, etc. Recently, electronic applications of MOFs like electrocatalysis, supercapacitors, batteries, electrochemical sensing, etc., have become a major research topic in MOF chemistry. However, the low electrical conductivity of most MOFs represents a major handicap in the development of these emerging applications. To overcome these limitations, different strategies have been developed to enhance electrical conductivity of MOFs for their implementation in electronic devices. In this review, we outline all these strategies employed to increase the electronic conduction in both intrinsically (framework-modulated) and extrinsically (guests-modulated) conducting MOFs., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

In this work, hollow CoS 2 particles were prepared by a one-step sulfurization strategy using polyoxometalate-based metal-organic frameworks as the precursor. The morphology and structure of CoS 2 have been monitored by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray powder diffraction. The mechanism for the formation of CoS 2 is discussed. The reaction time and sulfur content are found to be important factors that affect the morphology and pure phase formation of CoS 2 , and a hollow semioctahedral morphology of CoS 2 with open voids was obtained when the sulfur source was twice as large as the precursor and the reaction time was 24 h. The CoS 2 (24 h) particles show an excellent peroxidase-like activity for the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized (oxTMB) by hydrogen peroxide. The polyoxometalate used as a precursor helps to stabilize oxTMB during catalytic oxidation, forming a stable curve platform for at least 8 min. Additionally, the colorimetric detection of hydroquinone is developed with a low detection limit of 0.42 μM. This research provides a new strategy to design hollow materials with high peroxidase-mimicking activity.

Electronic and steric effects are known to greatly influence the structure, characteristics and reactivity of organic compounds. A typical π bond is weakened by oxidation (corresponding to the removal of electrons from bonding orbitals), by reduction (through addition of electrons to antibonding orbitals) and by unpairing of the bonding electrons, such as in the triplet state. Here we describe tetrafluorenofulvalene (TFF), a twisted, open-shell alkene for which these general rules do not hold. Through the synthesis, experimental characterization and computational analysis of its charged species spanning seven redox states, the central alkene bond in TFF is shown to become substantially stronger in the tri- and tetraanion, generated by chemical reduction. Furthermore, although its triplet state contains a weaker alkene bond than the singlet, in the quintet state its bond order increases substantially, yielding a flatter structure. This behaviour originates from the doubly bifurcated topology of the underlying spin system and can be rationalized by the balancing effects of benzenoid aromaticity and spin pairing., (© 2023. The Author(s).)

A new diradical based on diindenocarbazole or difluorenopyrrole was synthesized and experimentally characterized by optical, electrochemical, and magnetic techniques, as well as quantum chemical calculations. The isomerism of these structures tunes the diradical character and the associated properties, representing a unique case of such important modulation. A full study of the electronic structure was carried out considering the perturbative interactions between different canonical forms as well as the anti-aromatic character of the molecular cores. Such a study reveals how we can tune diradical character simply by reorganizing the bonding patterns at constant chemical costs (composition)., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)

Diradicaloid helicenes constructed formally by non-benzenoid double π-extension of phenanthrene were synthesized by a common strategy involving double electrophilic benzannulation. Steric effects in the second benzannulation step led to considerable structural diversity among the products, yielding a symmetrical dinor[7]helicene 1 and two isomeric unsymmetrical double helicenes 2 and 3, containing a nor[5]helicene and [4]helicene fragment, respectively, in addition to a common nor[6]helicene motif. Geometries, configurational dynamics, and electronic structure of these helicenes were analyzed using solid-state structures, spectroscopic methods, and computational analyses. The open-shell character of the singlet states of these helicenes increases in the order 3<1<2, with strongly varying diradicaloid indexes and singlet-triplet gaps. Compounds 1-3 displayed narrow optical gaps of 0.79-1.25 eV, resulting in significant absorption in the near infrared (NIR) region. They also exhibit reversible redox chemistry, each of them yielding stable radical cations, radical anions, and dianions, in some cases possessing intense NIR absorptions extending beyond 2500 nm., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We exploit the high versatility of the solvent ethylene glycol (eg = CH 2 OH-CH 2 OH) acting as a ligand with three different coordination modes: terminal (κ O ), chelate (κ 2 O,O' ), and bridge (1κ O ,2κ O' ) to prepare a novel family of six different coordination polymers with Dy III and three different anilato ligands (3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion = C 6 O 4 X 2 2- , with X = H, Cl, and Br). With the X = H derivative (dhbq 2- ), we have prepared [Dy 2 (dhbq) 3 (eg) 2 (μ-eg)]·4eg·2H 2 O ( 1 ), a 3D diamond-like network with a chelate and bridging eg molecules. With the X = Cl derivative (chloranilato), we have prepared [Dy 2 (C 6 O 4 Cl 2 ) 3 (eg) 4 ]·2eg·H 2 O ( 2 ) and [Dy 2 (C 6 O 4 Cl 2 ) 3 (μ-eg)(H 2 O) 4 ]·2eg·7H 2 O ( 3 ). Compound 2 has a 2D (6,3)-gon brick-wall lattice and contains a chelate and a terminal eg molecule. Compound 3 has a 3D diamond-like topology as 1 , although now the chelate eg has been replaced by two water molecules. Finally, with the X = Br derivative (bromanilato), we have obtained [Dy 2 (C 6 O 4 Br 2 ) 3 (eg) 2 (CH 3 OH) 2 ]·2eg·4CH 3 OH ( 4 ), [Dy 2 (C 6 O 4 Br 2 ) 3 (eg) 4 ]·4eg ( 5 ), and [Dy 2 (C 6 O 4 Br 2 ) 3 (eg) 3 (H 2 O)]·2eg·H 2 O ( 6 ). Compound 4 has a 2D (6,3)-gon herringbone topology and contains a chelate eg and a MeOH molecule. Compounds 5 and 6 have a 2D (6,3)-gon brick-wall topology with a chelate and a terminal eg molecules (in 5 and in one of the two independent Dy centers of 6 ). The other Dy center in 6 has a chelate eg and a water molecule. All the compounds show slow relaxation of the magnetization at low temperatures (in compounds 1 , 2 , and 5 with no applied DC field). The magnetization of compounds 1 - 6 relaxes through Orbach and direct mechanisms when a DC field is applied and through an Orbach and/or quantum tunneling mechanism when no DC field is applied., Competing Interests: The authors declare no competing financial interest., (© 2023 American Chemical Society.)

The optical, structural, and magnetic properties of iron(II,III) sandwich complexes, Fe(Tp') 2 n + (Tp' = bis(3,5-dimethylpyrazolyl)benzotriazolylborate), are described. The intensely colored Fe II (Tp') 2 (orange) and Fe III (Tp') 2 + (purple) show strong MLCT bands. Geometric isomerism for M(Tp') 2 is established crystallographically in the racemate of chiral cis -Fe(Tp') 2 . For the first time, paramagnetic 11 B NMR describes solution-phase low-spin (LS, S = 0) to high-spin (HS, S = 2) crossover behavior in Fe(Tp') 2 . Thermochemical parameters for solution-phase SCO of Fe(Tp') 2 demonstrate the endothermic LS to HS conversion and entropic preference of the HS state. Entropy changes for both Fe(Tp') 2 isomers are significantly larger than for the majority of iron scorpionate SCO systems. Solid-state magnetic and thermochemical measurements show cis -Fe(Tp') 2 to be thermally stable up to 520 K, allowing experimental investigation of a solid-state SCO magnetic hysteresis of over 45 K. A large solution vs solid-state SCO difference was observed: cis -Fe(Tp') 2 shows T c ≈ 270 K (solution) and T c ≈ 385 K (solid), with the remarkably wide Δ T c ≈ 115 K; trans -Fe(Tp') 2 shows T c ≈ 278 K (solution) and T c ≈ 372 K (solid). Solid-state T c values are among the highest seen for iron(II) molecular systems. The large solution/solid Δ T c difference is explained by "anchoring" intermolecular interactions in the solid state that prevent thermal expansion of the LS iron(II) coordination sphere in its transition to the HS state. DFT calculations, validated against LS cis -Fe(Tp') 2 crystallography and LS to HS SCO thermochemical parameters, demonstrate the role the benzotriazole rings play in its structural and optical properties. The Lewis basicity of M(Tp') 2 is shown with the structural characterization of the air-stable tin(II) adduct [ cis -Fe(Tp') 2 -SnCl 2 ]; tin(II) coordination does not alter the iron(II) spin state. The Tp' chelate adds functionality (asymmetry, chirality, chemical reactivity) to the array of iron SCO materials for potential incorporation into nanoscale magnetic switches and spintronic devices.

Four difluorenoheteroles having a central quinoidal core with the heteroring varying as furan, thiophene, its dioxide derivative and pyrrole have shown to be medium character diradicals. Solid-state structures, optical, photophysical, magnetic, and electrochemical properties have been discussed in terms of diradical character, variation of aromatic character and captodative effects (electron affinity). Organic field-effect transistors (OFETs) have been prepared, showing balanced hole and electron mobilities of the order of 10 -3  cm 2  V -1  s -1 or ambipolar charge transport which is first inferred from their redox amphoterism. Quantum chemical calculations show that the electrical behavior is originated from the medium diradical character which produces similar reorganization energies for hole and electron transports. The vision of a diradical as simultaneously bearing pseudo-hole and pseudo-electron defects might justify the reduced values of reorganization energies for both regimes. Structure-function relationships between diradical and ambipolar electrical behavior are revealed., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

In situ molecular transformation under hydrothermal conditions is a feasible method to introduce distinct organic ligands and suppress competitive reactions between different synthons. However, this strategy has not yet been explored for the preparation of polyoxometalate (POM)-encapsulated metal-organic frameworks (MOFs). In this work, we designed and prepared a new compound, [Co 2 (3,3'-bpy)(3,5'-bpp)(4,3'-bpy)](H 2 O) 3 [SiW 12 O 40 ] ( 1 ) (4,3'-bpy = 4,3'-dipyridine, 3,5'-bpp = 3,5'-bis(pyrid-4-yl)pyridine, and 3,3'-bpy = 3,3'-bis(pyrid-4-yl) dipyridine), via an in situ ligand synthesis route. The compound shows a novel POM-encapsulated MOF structure with two pairs of left- and right-handed double helixes. These left- and right-handed helical chains further lead to triangular and rhombus-like channels, respectively. Moreover, the as-synthesized title compound shows superior electrocatalytic activity toward the hydrogen evolution reaction (HER) in 1 M KOH aqueous solution with a low overpotential and Tafel slope of 92 mV and 92.1 mV dec -1 , respectively, under a current density of 10 cm -2 . Also, the compound exhibits a high activity for the photocatalytic degradation of the dye rhodamine B. The excellent performance of the compound may be attributed to the synergistic effect between W and Co elements and the presence of encapsulated POMs. The title compound proves that it is possible to prepare multifunctional MOFs with POMs and transition metals showing HER activity and dye degradation activity.

To develop high-performance supercapacitors, the negative electrode is at present viewed as one of the most challenging tasks for obtaining the next-generation of energy storage devices. Therefore, in this study, a polyoxometalate-based coordination polymer [Zn(itmb) 3 H 2 O][H 2 SiW 12 O 40 ]·5H 2 O (1) is designed and prepared by a simple hydrothermal method for constructing a high-capacity negative electrode. Polymer 1 has two water-assisted proton channels, which are conducive to enhancing the electrical conductivity and storage capacity. Then, MXene Ti 3 C 2 T x is chosen to accommodate coordination polymer 1 as the interlayer spacers to improve the conductivity and cycling stability of 1, while preventing the restacking of MXene. Expectedly, the produced composite electrode 1@Ti 3 C 2 T x shows an excellent specific capacitance (1480.1 F g -1 at 5 A g -1 ) and high rate performance (a capacity retention of 71.5% from 5 to 20 A g -1 ). Consequently, an asymmetric supercapacitor device is fabricated using 1@Ti 3 C 2 T x as the negative electrode and celtuce leaves-derived carbon paper as the positive electrode, which demonstrates ultrahigh energy density of 32.2 Wh kg -1 , and power density 2397.5 W kg -1 , respectively. In addition, the ability to illuminate a red light-emitting diode for several minutes validates its feasibility for practical application., (© 2022 Wiley-VCH GmbH.)

This research raises the potential use of coordination polymers as new useful materials in two essential research fields, allowing the obtaining of a new multiartificial enzyme with the capacity to inhibit the growth of bacteria resistance. The fine selection of the ligands allows the design of a new 2D coordination polymer (CP), with the formula [Cu 2 (IBA) 2 (OH 2 ) 4 ] n ·6nH 2 O, by the combination of Cu (II) as the metal center with a pseudoamino acid (H 2 IBA = isophthaloyl bis β -alanine). Quantitative total X-ray fluorescence (TXRF) analyses show that the obtained CP can gradually release Cu (II) ions. Additionally, this CP can be nanoprocessed and transformed into a metal-organic gel (MOG) by using different Cu (II) salt concentrations and the application of ultrasounds. Considering its nanometric dimensions, the slow Cu (II) release and its simple processability, its performance as an artificial enzyme, and its antibacterial ability were explored. The results obtained show the first nanocoordination polymer acting as an artificial multienzyme (peroxidase, catalase, and superoxodismutase) exhibiting antibacterial activity in the presence of hydrogen peroxide, with selective behavior for three bacterium strains ( S. spiritovirum, A. faecales, and B. cereus ). Indeed, this CP shows a more robust inhibition capacity for Sphingobacterium . Going beyond that, as there are no comfortable and practically clinical tests capable of detecting the presence of Sphingobacteria , the compound can be easily embedded to form moldable gelatin that will facilitate the handling and low-cost commercial kits., Competing Interests: The authors declare that there are no conflicts of interest., (Copyright © 2022 Noelia Maldonado et al.)

The synthesis, characterization, crystal structure and detailed magnetic properties of a pyrazine (pyz) and azido (N 3 ) bridged cobalt(II) compound of formula [Co(N 3 ) 2 (pyz)] (1) are reported. Compound 1 shows a layered structure formed by Co(II) chains with double μ-N 3 (κN 1 ,N 1 ) bridges that are further connected by μ-(pyrazine-κN 1 ,N 4 ) bridges. The layers present weak van der Waals interactions between azido terminal groups. The magnetic properties show the presence of a metamagnetic behaviour in 1 with two critical fields of 200 and 400 mT at low temperatures. AC magnetic measurements show the presence of a long-range 2D ferromagnetic order at T c ≈ 8.0-7.0 K for dc fields above 200 mT and a long-range 3D ferromagnetic order at T c ≈ 4.5 K for dc fields above 400 mT.

This work contributes to enlightening the opportunities of the anisotropic scheme of non-covalent interactions present in supramolecular materials. It provides a top-down approach based on their selective disruption that herein has been employed to process a conventional microcrystalline material to a nanofibrillar porous material. The developed bulk microcrystalline material contains uracil-1-propionic acid (UPrOH) nucleobase as a molecular recognition capable building block. Its crystal structure consists of discrete [Cu(UPrO) 2 (4,4'-bipy) 2 (H 2 O)] (4,4'-bipy=4,4'-bipyridine) entities held together through a highly anisotropic scheme of non-covalent interactions in which strong hydrogen bonds involving coordinated water molecules provide 1D supramolecular chains interacting between them by weaker interactions. The sonication of this microcrystalline material and heating at 45 °C in acetic acid-methanol allows partial reversible solubilization/recrystallization processes that promote the cross-linking of particles into an interlocked platelet-like micro-particles metal-organic gel, but during CO 2 supercritical drying, the microcrystalline particles undergo a complete morphological change towards highly anisotropic nanofibers. This unprecedented top-down microstructural conversion provides a nanofibrillar material bearing the same crystal structure but with a highly increased surface area. Its usefulness has been tested for HPLC separation purposes observing the expected nucleobase complementarity-based separation.

A hexaradicaloid molecule with alternating Kekulé and non-Kekulé connectivities between adjacent spin centers was obtained by fusing two conjugation motifs in Chichibabin and Schlenk hydrocarbons into a coronoid structure. 1 H NMR, ESR, and SQUID experiments and computational analyses show that the system has a singlet ground state with a significant hexaradicaloid character (γ 0 =0.826, γ 1 =γ 2 =0.773). It has multiple thermally accessible high-spin states (up to the septet), with uniform energy gaps of ca 1.0 kcal mol -1 between consecutive multiplicities. In line with its open-shell character, the coronoid has a small electronic band gap (ca. 0.8 eV) and undergoes two consecutive one-electron oxidations at low potentials, yielding cationic forms with extended near-infrared absorption. The hexaradicaloid, which combines open-shell and macrocyclic contributions to its π conjugation, is an example of a design strategy for multistate spin switches and redox-amphoteric NIR dyes., (© 2021 Wiley-VCH GmbH.)

We examine the effects of fusing two benzofurans to s-indacene (indacenodibenzofurans, IDBFs) and dicyclopenta[b,g]naphthalene (indenoindenodibenzofurans, IIDBFs) to control the strong antiaromaticity and diradical character of these core units. Synthesis via 3-functionalized benzofuran yields syn-IDBF and syn-IIDBF. syn-IDBF possesses a high degree of paratropicity, exceeding that of the parent hydrocarbon, which in turn results in strong diradical character for syn-IIDBF. In the case of the anti-isomers, synthesized via 2-substituted benzofurans, these effects are decreased; however, both derivatives undergo an unexpected ring-opening reaction during the final dearomatization step. All the results are compared to the benzothiophene-fused analogues and show that the increased electronegativity of oxygen in the syn-fused derivatives leads to enhancement of the antiaromatic core causing greater paratropicity. For syn-IIDBF increased diradical character results from rearomati-zation of the core naphthalene unit in order to relieve this paratropicity., (© 2021 Wiley-VCH GmbH.)

This work is focused on the rational structural design of two isostructural Cu(II) nano-coordination polymers (NCPs) with uracil-1-acetic acid (UAcOH) ( CP1n ) and 5-fluorouracil-1-acetic acid ( CP2n ). Suitable single crystals for X-ray diffraction studies of CP1 and CP2 were prepared under hydrothermal conditions, enabling their structural determination as 1D-CP ladder-like polymeric structures. The control of the synthetic parameters allows their processability into water colloids based on nanoplates ( CP1n and CP2n ). These NCPs are stable in water at physiological pHs for long periods. However, interestingly, CP1n is chemically altered in culture media. These transformations provoke the partial release of its building blocks and the formation of new species, such as [Cu(UAcO) 2 (H 2 O) 4 ]·2H 2 O ( Cu(II)-complex ), and species corresponding to the partial reduction of the Cu(II) centers. The cytotoxic studies of CP1n versus human pancreatic adenocarcinoma and human uveal melanoma cells show that CP1n produces a decrease in the cell viability, while their UAcOH and Cu(II) - complex are not cytotoxic under similar conditions. The copper reduction species detected in the hydrolysis of CP1n are closely related to the formation of the reactive oxygen species (ROS) detected in the cytotoxic studies. These results prompted us to prepare CP2n that was designed to improve the cytotoxicity by the substitution of UAcO by 5-FUAcO, taking into account the anticancer activity of the 5-fluorouracil moiety. The new CP2n has a similar behavior to CP1n both in water and in biological media. However, its subtle structural differences are vital in improving its cytotoxic activity. Indeed, the release during the hydrolysis of species containing the 5-fluorouracil moiety provokes a remarkable increase in cellular toxicity and a significant increase in ROS species formation.

1,2-Bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L) reacts with [Cu(OAc) 2 ] and C 6 H 5 COOH, 4-OH-C 6 H 4 COOH, 2-Cl-C 6 H 4 COOH and (3,5-NO 2 ) 2 -C 6 H 3 COOH to afford the copper complexes [Cu 2 (C 6 H 5 COO) 4 (L) 2 ] (1), [Cu 2 (4-OH-C 6 H 4 COO) 4 (L) 2 ] (2), [Cu 2 (2-Cl-C 6 H 4 COO) 4 (L) 2 ] n (3) and [Cu{(3,5-NO 2 ) 2 -C 6 H 3 COO} 2 L] n (4) which are characterised by IR, mass spectrometry, elemental analyses, and X-ray crystallography. The structural data revealed two geometries that are adopted by the complexes: (i) paddle wheel in 1, 2·7H 2 O, 3 and (ii) regular chains in 3 and 4. Magnetic studies show strong antiferromagnetic couplings in the paddle wheel complexes and a weak antiferromagnetic coupling in the monometallic chain one. Catalysis studies performed with these complexes (1-4) showed that they initiate ring opening polymerization (ROP) of ε-caprolactone (ε-CL) under solvent-free conditions and d,l-lactide in toluene at elevated temperatures. Polycaprolactone (PCL) and poly(d,l-lactide) (PLA) obtained from the polymerization reactions are of low molecular weights (858 for PCL and 602 Da for PLA for initiator 1) and polydispersity indices (typically 2.16 for PCL and 1.64 for PLA with 1 as the initiator). End group analysis of the polymers, determined by MALDI-ToF MS, indicates that the polymers have benzoate, hydroxyl, methoxy and cyclic end groups., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The combination of Co(III) and Dy(III) with a compartmental Schiff base ligand (H 3 L=3-[(2-Hydroxy-3-methoxy-benzylidene)-amino]-propane-1,2-diol), presenting three different coordinating pockets, has allowed the synthesis of two novel Co(III)-Dy(III) complexes: [Co 2 Dy(HL) 4 ]NO 3  ⋅ 2CH 3 CN (1), a rare example of trinuclear linear Co III 2 Dy III complex (and the first with slow relaxation of magnetization in absence of a DC field) and [Co 2 Dy 2 (μ 3 -OH) 2 (HL) 2 (OAc) 6 ] ⋅ 4.6H 2 O (2), the first tetranuclear Co III 2 Dy III 2 cluster with a rhomb-like structure where the Co(III) ions are connected along the short diagonal of the rhomb. 1 presents two different relaxation processes: a fast relaxation dominated by Quantum tunnelling (QT) and a slow relaxation with an energy barrier of 40 K. 2 shows two close relaxation processes without applied DC fields that follow QT and Orbach mechanisms whereas for H DC =500 Oe, the QT is cancelled and a direct term appears. Here we present the synthesis, X-ray structure and magnetic characterization of these two Co(III)-Dy(III) single-ion/molecule magnets., (© 2021 Wiley-VCH GmbH.)

The search for two- and three-dimensional materials with slow relaxation of the magnetization (single-ion magnets, SIM and single-molecule magnets, SMM) has become a very active area in recent years. Here we show how it is possible to prepare two-dimensional SIMs by combining Dy(III) with two different anilato-type ligands (dianions of the 3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone: C 6 O 4 X 2 2- , with X = H and Cl) in dimethyl sulfoxide (dmso). The two compounds prepared, formulated as: [Dy 2 (C 6 O 4 H 2 ) 3 (dmso) 2 (H 2 O) 2 ]·2dmso·18H 2 O ( 1 ) and [Dy 2 (C 6 O 4 Cl 2 ) 3 (dmso) 4 ]·2dmso·2H 2 O ( 2 ) show distorted hexagonal honeycomb layers with the solvent molecules (dmso and H 2 O) located in the interlayer space and in the hexagonal channels that run perpendicular to the layers. The magnetic measurements of compounds 1 , 2 and [Dy 2 (C 6 O 4 (CN)Cl) 3 (dmso) 6 ] ( 3 ), a recently reported related compound, show that the three compounds present slow relaxation of the magnetization. In compound 1 the SIM behaviour does not need the application of a DC field whereas 2 and 3 are field-induced SIM (FI-SIM) since they show slow relaxation of the magnetization when a DC field is applied. We discuss the differences observed in the crystal structures and magnetic properties based on the X group of the anilato ligands (H, Cl and Cl/CN) in 1 - 3 and in the recently reported derivative [Dy 2 (C 6 O 4 Br 2 ) 3 (dmso) 4 ]·2dmso·2H 2 O ( 4 ) with X = Br, that is also a FI-SIM.

We describe the synthesis and characterization of a new trinuclear Ni(ii) Schiff base complex of formula [Ni3(L)2(NCS)2(OAc)2(CH3OH)2] (1) where HL is the 1 : 1 condensation product of 2-picolylamine and o-vanillin. The crystal structure of complex 1 shows that the two terminal Ni(ii) ions are connected to the central one through a phenoxido- and a syn-syn acetato bridge, giving rise to a very bent configuration in the Ni3-core. Magnetic susceptibility measurements show the presence of a weak antiferromagnetic coupling with J = -3.22(2) cm-1. We also report a magneto-structural correlation, performed with all the magnetically characterized Ni(ii) trimers with similar bridges, showing a linear dependence between the J value and the dihedral angle (θ) between the planes containing the Ni-O-Ni and the carboxylate bridges. The super-exchange interaction is investigated by extensive density functional calculations within the broken symmetry approximation which show good agreement with the experimental data. The analysis of the spin density distribution and the shape of the magnetically active single occupied molecular orbitals (SOMO) provide a mechanism of exchange coupling through the bridging groups.

The crystal structure and magnetic properties of two mononuclear iron(iii) Schiff base complexes, [FeL 1 (NCS) 2 ] (1), HL 1 = 2-[1-[[2-[(2-aminoethyl)amino]ethyl]imino]ethyl]phenol and [FeL 2 (N 3 )Cl] (2), HL 2 = 2-(-1-(2-(2-aminoethylamino)ethylimino)ethyl)-4-methylphenol are reported. Each complex contains a Fe(iii) ion surrounded by a N 3 O Schiff base ligand and two NCS - ligands (in 1) or one N 3 - and one Cl - ligands (in 2). The magnetic properties can be well reproduced with zero field splittings in the high spin S = 5/2 Fe(iii) ions and weak intermolecular Fe-Fe interactions mediated by hydrogen bonds. This intermolecular antiferromagnetic interaction has been validated by using DFT calculations in complex 2. Moreover, the interaction energies of the H-bonded dimers in both complexes have been estimated using DFT calculations and characterized using a combination of QTAIM and NCI plot computational tools. Complexes 1 and 2 constitute two rare examples of Fe(iii) complexes with magnetic interactions through H-bonds., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Two dinuclear cobalt(ii) complexes, [(dmso)CoIIL1(μ-(m-NO2)C6H4COO)CoII(NCS)] (1) and [(dmso)CoIIL2(μ-(m-NO2)C6H4COO)CoII(NCS)] (2) [dmso = dimethylsulfoxide, H2L1 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol) and H2L2 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol)] have been synthesized and structurally characterized by single-crystal X-ray diffraction, magnetic-susceptibility measurements and various spectroscopic techniques. Each complex contains a cobalt(ii) center with a slightly distorted octahedral geometry and a second cobalt(ii) center with a distorted trigonal prismatic one. To obtain insight into the physical nature of weak non-covalent interactions, we have extensively used the Bader's quantum theory of atoms-in-molecules (QTAIM). In addition, the non-covalent interaction reduced density gradient (NCI-RDG) methods established the presence of such non-covalent intermolecular interactions. Variable temperature magnetic susceptibility measurements show that both cobalt centers in each complex are in the high spin state (S = 3/2) and both complexes show weak ferromagnetic couplings through the double phenoxido bridges (J = 3.36(3) cm-1 in 1 and 4.56(2) cm-1 in 2). The magnetic properties of both complexes can be fitted to a Co(ii) dimer model including similar orbital reduction factors (α = -0.94(1) for 1 and -0.85(1) for 2) although different zero field splitting parameters D(1) = 11.0(4) cm-1 and D(2) = 19.5(4) cm-1 in 1 and D(1) = 8.2(4) cm-1 and D(2) = -1.3(4) cm-1 in 2. AC magnetic measurements reveal that the CoII2 unit in complex 2 exhibits field-induced slow relaxation of the magnetization at low temperatures and high frequencies.

The preparation of a series of dibenzo- and tetrabenzo-fused fluoreno[3,2- b ]fluorenes is disclosed, and the diradicaloid properties of these molecules are compared with those of a similar, previously reported series of anthracene-based diradicaloids. Insights on the diradical mode of delocalization tuning by constitutional isomerism of the external naphthalenes has been explored by means of the physical approach (dissection of the electronic properties in terms of electronic repulsion and transfer integral) of diradicals. This study has also been extended to the redox species of the two series of compounds and found that the radical cations have the same stabilization mode by delocalization that the neutral diradicals while the radical anions, contrarily, are stabilized by aromatization of the central core. The synthesis of the fluorenofluorene series and their characterization by electronic absorption and vibrational Raman spectroscopies, X-ray diffraction, SQUID measurements, electrochemistry, in situ UV-vis-NIR absorption spectroelectrochemistry, and theoretical calculations are presented. This work attempts to unify the properties of different series of diradicaloids in a common argument as well as the properties of the carbocations and carbanions derived from them.

Thiele (Th) and tetrabenzo-Chichibabin (TBC) derivatives with terminal dibenzocycloheptatriene (DBHept) units were prepared. A clear correlation between their electronic and molecular structures was stablished. Insights into their closed- or open-shell ground states were gained, where particular contribution of the heptagonal carbocycles as end-groups was proved. Remarkably, a thermally accessible triplet diradical configuration was confirmed for the DBHept-TBC compound.

A series of multifunctional 2D frameworks prepared with Dy(iii) and the bromanilato ligand, formulated as: [Dy 2 (C 6 O 4 Br 2 ) 3 (G) n ]·nG with G = H 2 O, dimethylformamide (dmf) and dimethylsulfoxide (dmso), can exchange the coordinated and non-coordinated solvent molecules (G) in a reversible way. These multifunctional frameworks show field induced slow relaxation of the magnetization and luminescence that can be easily and reversibly modified by solvent exchange.

The combination of two 8-aminoquinoline-based Schiff base ligands (L1 and L2) with SCN - and Ni(II) has led to the synthesis of two new one-dimensional thiocyanato-bridged coordination polymers: [Ni(L1)(NCS) 2 ] n ( 1 ) and [Ni(L2)(NCS) 2 ] n ( 2 ). Both compounds are isostructural and consists of regular zigzag thiocyanato-bridged chains with very weak S···S interchain interactions. The measured room-temperature conductivities of compounds 1 and 2 (7.0 × 10 -5 and 2.0 × 10 -5 S m -1 , respectively) are indicative of semiconductor behavior which increases in the presence of photoillumination (3.5 × 10 -4 and 4.9 × 10 -4 S m -1 , respectively). The measured I - V characteristics of compound 1 and 2 based thin film metal-semiconductor (MS) junction devices under irradiation and nonirradiation conditions show a nonlinear rectifying behavior, typical of a Schottky diode (SD). The rectification ratios ( I on / I off ) of the SDs in the dark at ±2 V (26.96 and 31.96 for 1 - and 2 -based devices, respectively) increase to 44.19 and 79.42, respectively, upon light irradiation. The photoinduced behavior has been analyzed by thermionic emission theory, and to determine the diode parameters, the Cheung's method has been employed. These diode parameters indicate that compound 2 has a better performance in comparison to compound 1 and that these materials are good candidates for applications in electrochemical devices. Magnetic measurements show that both compounds present ferromagnetic Ni-Ni intrachain and weak antiferromagnetic interchain interactions. The isothermal magnetizations at 2 K show that both compounds are metamagnets with critical fields of ca. 130 mT in 1 and 90 mT in 2 at 2 K. In the ferromagnetic phase (above the critical field), both compounds exhibit a long-range ferromagnetic order with critical temperatures of around 3.5 K in 1 and 3.0 K in 2 . DC and AC measurements with different applied DC fields confirm the metamagnetic behaviors and have allowed the determination of the magnetic phase diagram in both compounds.

The development of a negative electrode for supercapacitors is a critical challenge for the next-generation of energy-storage devices. Herein, two new electrodes formed by the coordination polymers [Ni(itmb) 4 (HPMo 12 O 40 )]·2H 2 O (1) and [Zn(itmb) 3 (H 2 O)(HPMo 12 O 40 )]·4H 2 O (2) (itmb = 1-(imidazo-1-ly)-4-(1,2,4-triazol-1-ylmethyl)benzene), synthesized by a simple hydrothermal method, are described. Compounds 1 and 2 show high capacitances of 477.9 and 890.2 F g -1 , respectively. An asymmetric supercapacitor device assembled using 2 which has novel water-assisted proton channels as negative electrode and active carbon as positive electrode shows ultrahigh energy density and power density of 23.4 W h kg -1 and 3864.4 W kg -1 , respectively. Moreover, the ability to feed a red light emitting diode (LED) also demonstrates the feasibility for practical use. The results allow a better elucidation of the storage mechanism in polyoxometalate-based coordination polymers and provide a promising direction for exploring novel negative materials for new-generation high-performance supercapacitors., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metal-ligand coordination interactions are usually much stronger than weak intermolecular interactions. Nevertheless, here, we show experimental evidence and theoretical confirmation of a very rare example where metal-ligand bonds dissociate in an irreversible way, helped by a large number of weak intermolecular interactions that surpass the energy of the metal-ligand bond. Thus, we describe the design and synthesis of trinuclear Mn 2 Fe complex {[Mn(L)(H 2 O)] 2 Fe(CN) 6 }, 2- starting from a mononuclear Mn(III)-Schiff base complex: [Mn(L)(H 2 O)Cl] ( 1 ) and [Fe(CN) 6 ] 4- anions. This reaction implies the dissociation of Mn(III)-Cl coordination bonds and the formation of Mn(III)-NC bonds with the help of several intermolecular interactions. Here, we present the synthesis, crystal structure, and magnetic characterization of the monomeric Mn(III) complex [Mn(L)(H 2 O)Cl] ( 1 ) and of compound (H 3 O)[Mn(L)(H 2 O) 2 ]{[Mn(L)(H 2 O)] 2 Fe(CN) 6 } · 4H 2 O ( 2 ) (H 2 L = 2,2'-((1 E ,1' E )-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(4-methoxyphenol)). Complex 1 is a monomer where the Schiff base ligand (L) is coordinated to the four equatorial positions of the Mn(III) center with a H 2 O molecule and a Cl - ion at the axial sites and the monomeric units are assembled by π-π and hydrogen-bonding interactions to build supramolecular dimers. The combination of [Fe(CN) 6 ] 4- with complex 1 leads to the formation of linear Mn-NC-Fe-CN-Mn trimers where two trans cyano groups of the [Fe(CN) 6 ] 4- anion replace the labile chloride from the coordination sphere of two [Mn(L)(H 2 O)Cl] complexes, giving rise to the linear anionic {[Mn(L)(H 2 O)] 2 Fe(CN) 6 } 2- trimer. This Mn 2 Fe trimer crystallizes with an oxonium cation and a mononuclear [Mn(L)(H 2 O) 2 ] + cation, closely related to the precursor neutral complex [Mn(L)(H 2 O)Cl]. In compound 2 , the Mn 2 Fe trimers are assembled by several hydrogen-bonding and π-π interactions to frame an extended structure similar to that of complex 1 . Density functional theoretical (DFT) calculations at the PBE1PBE-D3/def2-TZVP level show that the bond dissociation energy (-29.3 kcal/mol) for the Mn(III)-Cl bond is smaller than the summation of all the weak intermolecular interactions (-30.1 kcal/mol). Variable-temperature magnetic studies imply the existence of weak intermolecular antiferromagnetic couplings in both compounds, which can be can cancelled with a critical field of ca. 2.0 and 2.5 T at 2 K for compounds 1 and 2 , respectively. The magnetic properties of compound 1 have been fit with a simple S = 2 monomer with g = 1.959, a weak zero-field splitting (| D | = 1.23 cm -1 ), and a very weak intermolecular interaction ( zJ = -0.03 cm -1 ). For compound 2 , we have used a model with an S = 2 monomer with ZFS plus an S = 2 antiferromagnetically coupled dimer with g = 2.009, | D | = 1.21 cm -1 , and J = -0.42 cm -1 . The metamagnetic behavior of both compounds is attributed to the weak intermolecular π-π and hydrogen-bonding interactions.

Inclusion of quinoidal cores in conjugated hydrocarbons is a common strategy to modulate the properties of diradicaloids formed by aromaticity recovery within the quinoidal unit. Here we describe an alternative approach of tuning of diradical properties in indenoindenodibenzothiophenes upon anti → syn isomerism of the benzothiophene motif. This alters the relationship of the S atom with the radical center from linear to cross conjugation yet retains the same 2,6-naphtho conjugation pattern of the rearomatized core. We conduct a full comparison between the anti and syn derivatives based on structural, spectroscopic, theoretical, and magnetic measurements, showing that these systems are stable open-shell singlet diradicaloids that only access their triplet state at elevated temperatures.

Fluoreno[2,1-a]fluorene, a molecule comprising fused ortho-quinodimethane units in a 1,5-napthoquinodimethane core, has been prepared and investigated with spectroscopy (UV-Vis-NIR, 1 H-NMR and Raman), SQUID magnetometry, spectroelectrochemistry and quantum chemistry. While para-quinodimethanes with a 2,6-substitution pattern exist as closed-shell species and meta-quinodimethanes with 2,7-substitution favour a ground electronic state with very large diradical character, our 1,5-substituted ortho-naphthoquinodimethane-based system exhibits an intermediate degree of diradical character.

To investigate the relationship between the structures of polyoxometalate host-guest materials and their energy-storage performance, three novel polyoxometalate-based metal-organic compounds, [Ag 10 (C 2 H 2 N 3 ) 8 ][HVW 12 O 40 ], [Ag 10 (C 2 H 2 N 3 ) 6 ][SiW 12 O 40 ], and [Ag(C 2 H 2 N 3 )][Ag 12 (C 2 H 2 N 3 ) 9 ][H 2 BW 12 O 40 ] are synthesized by a one-step hydrothermal method and further confirmed by single-crystal X-ray diffraction analyses and other numerous characterization techniques. In compound [Ag 10 (C 2 H 2 N 3 ) 8 ][HVW 12 O 40 ], the Keggin clusters are intersected into channels formed by a 3D open metal-organic framework. In contrast, in compounds [Ag 10 (C 2 H 2 N 3 ) 6 ][SiW 12 O 40 ] and [Ag(C 2 H 2 N 3 )][Ag 12 (C 2 H 2 N 3 ) 9 ][H 2 BW 12 O 40 ], the Keggin clusters are encapsulated into silver-triazole metal-organic nanocages to construct core-shell structures, which are further fused together by covalent bonds to form 3D polyoxometalate-based metal-organic frameworks. The electrochemical properties of three compound-based electrodes are estimated by cyclic voltammetry, galvanostatic charge-discharge, electrochemically active surface area, and electrochemical impedance spectroscopy. The results of the electrochemical performance tests indicate that these compounds possess high specific capacitance and cycling stability, especially [Ag 10 (C 2 H 2 N 3 ) 8 ][HVW 12 O 40 ], showing a specific capacitance of 93.5 F g -1 , which is higher than that of many other polyoxometalate-based electrode materials. A possible mechanism of the electrochemical performance is explored, which is mainly related to the redox capacity of polyoxometalate, the electrochemically active surface area, the electrochemical impedance spectroscopy, and the microstructures of polyoxometalate-based metal-organic frameworks.

Two tetranuclear mixed-valence cobalt(III/II) complexes having the general formula [(μ 1,3 -N 3 ){Co II (L n )(μ-O 2 CC 6 H 4 NO 2 )Co III (N 3 )} 2 ]PF 6 (where H 2 L 1 and H 2 L 2 are two reduced Schiff base ligands) have been synthesized and characterized. The structures of both complexes show cobalt(II) and cobalt(III) centers with a distorted octahedral geometry with cobalt(III) and cobalt(II) centers located at the inner N 2 O 2 and outer O 4 cavities of the reduced Schiff base ligands, respectively. The oxidation states of both cobalt centers have been confirmed by bond valence sum (BVS) calculations. The magnetic properties show that both compounds behave as cobalt(II) dimers connected through an end-to-end azido bridging ligand and show moderate antiferromagnetic Co(II)-Co(II) couplings of -11.0 and -14.4 cm -1 for 1 and 2 , respectively, as also corroborated by DFT calculations, J theo = -13.07 cm -1 for 1 and -12.49 cm -1 for 2 . The calculated spin densities of both complexes at the cobalt(II) centers are -2.75 and +2.75, respectively, clearly supporting that they are the magnetic centers., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)

In this work, three mono- and bidimensional coordination polymers (CPs) based on Cu(II) and Cu(I) ([Cu 2 (TAcO) 2 (C 2 O 4 )(4,4'-bpy)]·4H 2 O (CP1), [Cu 2 (UAcO) 2 (C 2 O 4 )(4,4'-bpy)]·2H 2 O (CP2) and [Cu 2 (TAcO) 2 (4,4'-bpy)] (CP3)), decorated with thymine and uracil-1-acetate (TAcO and UAcO), 4,4'-bipyridine (4,4'-bpy) and oxalate are synthetized. The supramolecular structures of the CPs are based on the formation of non-canonical hydrogen bonds established between the free moieties of nucleobases. Interestingly, the presence of Cu(II) centers provide for compound CP1, magnetism and semiconducting properties. Additionally, CP1 has been doped with iodine, increasing its electrical conductivity up to two orders of magnitude. Moreover, the size of the materials can be modulated from millimeters to the nanoscale, depending on the crystallization conditions and/or using ultrasound., (Published by Elsevier Inc.)

We report the synthesis and characterization of six novel heterometallic molecule-based 2D magnets with the bromanilato ligand (C 6 O 4 Br 2 2- = 1,3-dibromo-2,5-dihydroxy-1,4-benzoquinone dianion) and six different benzene derivative molecules. The compounds, formulated as (NBu 4 )[MnCr(C 6 O 4 Br 2 ) 3 ]·1.75C 6 H 5 Br (1), (NBu 4 )[MnCr(C 6 O 4 Br 2 ) 3 ]·C 6 H 5 X with X = Cl (2), I (3) and CH 3 (4) and (NBu 4 )[MnCr(C 6 O 4 Br 2 ) 3 ]·2C 6 H 5 X with X = CN (5) and NO 2 (6), present the classical hexagonal honeycomb-(6,3) lattice with alternating Mn(ii) and Cr(iii) ions. The layers are packed in an eclipsed way along the a direction giving rise to hexagonal channels where the benzene derivative molecules are located with π-π interactions between the benzene and anilato rings. The interlayer space contains the NBu 4 + cations needed to compensate the anionic charge of the [Mn II Cr III (C 6 O 4 Br 2 ) 3 ] - layers. The Mn-Cr exchange coupling through the bromanilato ligands is antiferromagnetic, leading to a long range ferrimagnetic order in the six compounds with ordering temperatures around 10 K. These ordering temperatures can be slightly modified in the range 9.5-11.4 K by simply changing the benzene-derivative solvent molecule. Here we discuss the possible structural and electronic reasons for this tuning effect of the solvent molecule and the important structural role played by the solvent molecules. We also show that it is possible to exchange the solvent molecules inside the hexagonal channels post-synthetically causing a tiny change in the ordering temperature and coercive field. Furthermore, we also show that it is possible to further change the ordering temperatures by simply removing the solvent molecules by heating the sample at low pressures to obtain a de-solvated phase.

A new multidentate ligand (H 3 L) was synthesized by the condensation reaction of 4-tert-butyl-2,6-diformylphenol and 2-amino-4-nitrophenol. The reaction of the ligand with hydrated lanthanide nitrate produced two isostructural trinuclear coordination clusters: [DyLn 3 L 3 (DMF) 3 (H 2 O) 2 ] ⋅ 3.8DMFLn=Dy (1) and Nd (2) (DMF=N, N-dimethylformamide). Single-crystal X-ray diffraction analysis revealed that there are three lanthanide ions arranged in an almost perfect linear fashion in both complexes. Magnetic studies show single-molecule-magnet (SMM) behavior in the Dy derivative with τ 0 =1.7×10 -6  s and a thermal energy barrier of 7.0 cm -1 . Both complexes were used as catalysts towards the Friedel-Crafts alkylation reaction of indole with different aldehydes with yields varying from 59-98 %. Complex 1 showed better catalytic efficiency than complex 2. This is the first report of using trinuclear lanthanide coordination clusters as catalysts for the Friedel-Crafts alkylation reaction., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We present a new example of a mononuclear iron(ii) complex exhibiting a correlated spin-crossover (SCO) transition and strong fluorescence, whose coordination sphere is saturated, for the first time, by six phosphorescent ligands. The interplay between SCO and light emission properties in the thermal region of the spin transition was investigated by means of magnetic, fluorescence, optical absorption and optical microscopy measurements on a single crystal. Overall, the results show an excellent correlation between fluorescence and magnetic data of the present gradual transition, indicating an extreme sensitivity of the optical activity of the ligand to the spin state of the active iron(ii) ions. These results open the way for conceiving new prototypes of pressure and temperature sensors based on this synergy between SCO and luminescence properties. In particular, the fact that cooperative SCO material is not a prerequisite for obtaining such synergetic effects, is useful for the design of thin films or nanoparticles, in which the cooperativity is reduced, for appropriate implementation in nanosized devices to enhance the sensing properties at the nanoscale.

Two new copper(ii) polymeric complexes, {[Cu(HPymat)(H2O)](NO3)}n (1) and [Cu2(Pymat)2(H2O)3]n (2), have been synthesized using the Schiff base ligand H2Pymat [H2Pymat = (E)-2-(1-(pyridin-2-yl)-methyleneamino)terephthalic acid]. Complex 1 is a cationic 1D polymer, whereas complex 2 is a two dimensional polymer. Both complexes were crystallographically, spectroscopically and magnetically characterized. Theoretical studies were performed and the catecholase activity of the complexes was also examined. Complex 1 is a ferromagnetically coupled complex with J = 2.8 cm-1 and 2 shows antiferromagnetic coupling with J = -1.6 cm-1. Both complexes show notable features in the EPR study. They show rhombic spectra at 77 K in the solid state, but by varying the temperature or solvents the nature of the spectra can be changed or inverted. This behaviour indicates a change of the ground state from dx2-y2 to dz2 orbitals. Theoretical calculations of 1 focus on the evaluation and characterization of interesting anion-π-anion assemblies that are formed in the solid state. In 2 we have analysed the unconventional chelate ringchelate ring π-stacking interactions that govern its solid state architecture. Both complexes act as functional models and show catechol oxidase activity with a kcat value of the order of 103 h-1.

Many qualitative structure-property correlations between diradical character and emerging molecular properties are known. For example, the increase of diradical character further decreases the singlet-triplet energy gap. Here we show that inclusion of thiophenes within a quinoidal polycyclic hydrocarbon imparts appreciable diradical character yet retains the large singlet-triplet energy gap, a phenomenon that has no precedent in the literature. The low aromatic character of thiophene and its electron-rich nature are the key properties leading to these unique findings. A new indenoindenodibenzothiophene scaffold has been prepared and fully characterized by several spectroscopies, magnetic measurements, solid-state X-ray and state-of-the-art quantum chemical calculations, all corroborating this unique dichotomy between the diradical input and the emerging magnetic properties. New structure-property relationships such as these are not only extremely important in the field of diradical chemistry and organic electronics, but also provide new insights into the versatility of π-electron chemical bonding.

Two novel polyoxometalate (POM)-encapsulated metal-organic nanotube (MONT) framework crystalline materials with unprecedented copper-mixed ligands, HUST-200 and HUST-201, have been successfully synthesized by an effective synthesis strategy. The encapsulation not only provides a shield to increase the chemical stability, but also does not affect its catalytic activity, and, therefore, the crystalline materials are very active for HER (H + can diffuse easily through the pores of the MONTs). Remarkably, HUST-200 displays a low overpotential of 131 mV (catalytic current density is equal to 10 mA·cm -2 ). This work thus offers a new way for devising HER electrocatalysts with low cost using POM-encapsulated MONT frameworks.