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Two new compounds, (NH4)4[Cu7(Hmesox)6(H2O)8]∙10H2O (1) and [Ru(bpy)3]4[Cu7(Hmesox)6Cl2]Cl2∙2CH3CN∙12H2O (2), were prepared and their structures were solved by single-crystal X-ray diffraction (mesoxalic acid = dihydroxypropanedioic acid, H4mesox). The triply deprotonated mesoxalate anion acts as a chelating and bridging ligand with its carboxylate and alkoxide groups, forming the anionic heptanuclear copper(II) clusters [Cu7(Hmesox)6(H2O)8]4− and [Cu7(Hmesox)6Cl2]6− in 1 and 2, respectively. Variable temperature magnetic studies revealed antiferromagnetic interactions in 1 and the coexistence of ferro and antiferromagnetic interactions in 2. The [Ru(bpy)3]2+ cations provided luminescent properties to compound 2. [ABSTRACT FROM AUTHOR]

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, I2, 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 21st century materials. [ABSTRACT FROM AUTHOR]

A new Mannich base (2-(4-(2-hydroxy-3-methoxy-5-methylbenzyl)-piperazin-1-yl)methyl)-6-methoxy-4-ethylphenol (H2L) and its tetranuclear NiII complex [Ni4L2(μ1,1-Cl)2(H2O)4]Cl2 (compound 1) are characterised using single-crystal X-ray diffraction measurements. Compound 1 contains four different NiII centres in a rhombus-like structure. Two Ni atoms (Ni1 and Ni2) have a NiN2O4 coordination sphere, while the other two (Ni3 and Ni4) have a NiO4Cl2 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 (J1 = −6.6(1) cm−1) through the phenoxide bridge along the sides of the rhombus and ferromagnetic coupling (J2 = 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 H2O2 and the oxidation of o-aminophenol (OAP) produces 2-aminophenoxazin-3-one (APX) and H2O 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 Ni4-core to form a mononuclear NiII complex in the presence of the substrate (3,5-DTBC/OAP). This NiII complex is reduced to NiI 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, O2 is reduced to H2O2 while in the phenoxazinone synthase-like activity O2 produces H2O. 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. [ABSTRACT FROM AUTHOR]

We report a novel triangular trinuclear copper(II) complex with a central μ3-OH bridge, [(CuL)3(μ3-OH)(ClO4)2]·CH3OH·H2O (1), stabilised by the oxime-based Schiff base ligand, 3-(((5-bromothiophen-2-yl)methylene)hydrazineylidene)butan-2-one oxime (HL). Comprehensive characterization of 1 has been realised through different analytical and physical methods coupled with spectroscopic techniques. 1 has been structurally characterised by single crystal X-ray diffraction. The antiproliferative capacity of HL and 1 has been evaluated against human lung cancer cell line A549. Compound 1 shows promising efficacy in contrast to HL, which shows a limited cytotoxicity. Contrary to HL, 1 has distinctly impeded the proliferation of lung adenocarcinoma A549 cell lines in a dose-dependent way. Compound 1 has been employed as a potential therapeutic agent for promising cellular transformation of malevolent A549 cell lines. The programmed cell death mechanism of 1 reveals characteristic apoptotic changes in cellular morphology like chromatin condensation, fragmented nuclei, nuclear shrinkage along with blebbing, elevated number of nuclear body fragments and distorted nucleus, while round, clear edged, intact nucleus and uniformly stained round nuclei have been observed in the negative control. Variable-temperature magnetic studies show an antiferromagnetic Cu⋯Cu coupling of −44.6(2) cm−1. The g value as determined by EPR measurement of 1 in frozen N,N-dimethylformamide solution corroborates the experimental magnetic susceptibility values. [ABSTRACT FROM AUTHOR]

A dodecanuclear [Ni8Ca4] compound, [Ni8(L)8Ca4(CO3)4(dmf)5.5(H2O)6.5]·20H2O (1) (dmf = dimethylformamide) has been prepared by the reaction of a polydentate ligand (E)-2-(2-hydroxy-3-methoxybenzylidene)amino-4-nitrophenol (H2L) with NiCl2·6H2O, CaCl2·2H2O and Na2CO3 in dmf at room temperature. The solid-state molecular structure of compound 1 was determined by single crystal X-ray crystallography. Compound 1 consists of a [Ni8Ca4] coordination wheel with eight NiII ions and four CaII ions assembled by four carbonates and eight deprotonated L2− ligands. The asymmetric unit of compound 1 contains two NiII ions, one CaII ion, two coordinated deprotonated Schiff base ligands (L2−), one coordinated carbonate ion, two coordinated dmf molecules (one with occupancy of 0.36), two coordinated water molecules (one with occupancy 0.64). Compound 1 is the largest coordination cluster containing NiII and CaII ions reported to date. The magnetic properties of 1 show the presence of predominant antiferromagnetic interactions. The magnetic susceptibility and isothermal magnetization data can be well reproduced with: g = 2.145(1), J1 = 2.93(4) cm−1, J2 = −0.41(2) cm−1 and J3 = −5.66(4) cm−1. [ABSTRACT FROM AUTHOR]