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Antibiotic resistance is a significant global concern, necessitating the development of either new antibiotics or advanced delivery methods. With this in mind, we report on the synthesis and characterisation of a new family of Metal-Organic Frameworks (MOFs), OnG6 MOFs, designed to act as multi-drug carriers for bacterial infection treatment. OnG6 is based on the pro-drug 4,4'-azodisalicylic acid (AZDH 4 ), which in vivo produces two equivalents of para -aminosalicylic acid (ASA), a crucial drug for M. tuberculosis treatment. X-ray and computational studies revealed that OnG6 MOFs are mesoporous MOFs with etb topology and an [M 2 (AZD)] formula (M = Zn, OnG6-Zn; Mg, OnG6-Mg; Cu, OnG6-Cu; and Co, OnG6-Co), featuring 1-dimensional channel type pores of 25 Å diameter. OnG6 MOFs are the first reported MOFs bearing the ligand AZDH 4 , joining the family of mesoporous MOFs arranged in a honeycomb pattern. They absorb isoniazid (INH) and ciprofloxacin (CIPRO) with the former being a specific antibiotic for M. tuberculosis , and the latter being a broader-spectrum antibiotic. The stability of the MOFs and their capacity for antibiotic uptake depend on the nature of the metal ion, with OnG6-Mg demonstrating the highest drug absorption. The antimicrobial activity of these species was assessed against S. aureus and E. coli , revealing that the carriers containing CIPRO displayed optimal efficacy.

The use of 2-pyridyl oximes in metal complexes chemistry has been extensively investigated in the last few decades as a fruitful source of species with interesting magnetic properties. In this work, the initial combination of pyridine-2-amidoxime (pyaoxH 2 ) and 2-methyl pyridyl ketoxime (mpkoH) with isonicotinic acid (HINA) and 3,5-pyrazole dicarboxylic acid (H 3 pdc) has provided access to three new compounds, [Ni 4 (INA) 2 (pyaox) 2 (pyaoxH) 2 (DMF) 2 ] ( 1 ), [Co 5 (mpko) 6 (mpkoH) 2 (OMe) 2 (H 2 O)](ClO 4 ) 6 ( 2 ), and [Co 5 (OH)(Hpdc) 5 (H 2 pdc)] ( 3 ). 1 displays a square-planar metal topology, being the first example that bears simultaneously HINA and pyaoxH 2 in their neutral or ionic form. The neighbouring Ni 4 units in 1 are held together through strong intermolecular hydrogen bonding interactions, forming a three-dimensional supramolecular framework. 2 and 3 are mixed-valent Co 4 III Co II and Co 2 III Co II 3 compounds with a bowtie and trigonal bipyramidal metal topology, accordingly. Direct current and alternate current magnetic susceptibility studies revealed that the exchange interactions between the Ni II ions in 1 are ferromagnetic ( J = 1.79(4) cm -1 ), while 2 exhibits weak AC signals in the presence of a magnetic field. The syntheses, crystal structures, and magnetic properties of 1-3 are discussed in detail.

Metal-organic frameworks (MOFs) are promising multifunctional porous materials for biomedical and environmental applications. Here, we report synthesis and characterization of a new MOF based on the tetrahedral secondary building unit [Zn 4 O(CBAB) 3 ] n (NUIG4), where CBABH 2 = 4-((4-carboxybenzylidene)amino)benzoic acid. NUIG4 belongs to the family of MOFs with primitive cubic pcu topology, being a rare example with 4-fold interpenetration. The pore architecture enables unprecedentedly high doxorubicin (DOX) loading capacity (1955 mg DOX/g NUIG4) with pH-controlled release. Solid-state NMR and ab initio modeling confirmed formation of aromatic π-π stacking interactions between DOX and the framework. Preliminary cell-line experiments suggested a protective effect of NUIG4 on healthy HDF cells against DOX toxicity. NUIG4 also displays potential for adsorptive small-molecule gas separation, with a BET surface area of 1358 m 2 g -1 and high selectivity of 2.75 for C 2 H 2 over CO 2 .

The goal of this work is to model the nature of the chemical species [CdCl 2 (extractant) 2 ] that are formed during the solvent (or liquid-liquid) extraction of the toxic cadmium(II) from chloride-containing aqueous media using hydrophobic 2-pyridyl ketoximes as extractants. Our coordination chemistry approach involves the study of the reactions between cadmium(II) chloride dihydrate and phenyl 2-pyridyl ketoxime (phpaoH) in water-containing acetone. The reactions have provided access to complexes [CdCl 2 (phpaoH) 2 ]∙H 2 O ( 1 ∙H 2 O) and {[CdCl 2 (phpaoH)]} n ( 2 ); the solid-state structures of which have been determined by single-crystal X-ray crystallography. In both complexes, phpaoH behaves as an N , N '-bidentate chelating ligand. The complexes have been characterized by solid-state IR and Raman spectra, and by solution 1 H NMR spectra. The preparation and characterization of 1 ∙H 2 O provide strong evidence for the existence of the species [CdCl 2 (extractant) 2 ] that have been proposed to be formed during the liquid-liquid extraction process of Cd(II), allowing the efficient transfer of the toxic metal ion from the aqueous phase into the organic phase., Competing Interests: The authors declare no conflict of interest.

The use of pyridine-2-amidoxime (pyaoxH 2 ) in Ni chemistry has provided access to a dodecanuclear complex and a hexadecanuclear Ni cluster, namely [Ni 12 (pyaox) 6 (pyaoxH) 6 (MeOH) 2 Cl 2 ]Cl 4 ·5MeOH (1·5MeOH) and [Ni 16 (pyaox) 8 (pyaoxH) 8 (MeOH) 4 ](SO 4 ) 4 ·10H 2 O·26MeOH (2·10H 2 O·26MeOH). Complex 1·5MeOH was isolated by the reaction of NiCl 2 ·6H 2 O, pyaoxH 2 and NaOMe in a 1 : 1 : 2 molar ratio in MeOH in 60% yield. Treatment of NiSO 4 ·6H 2 O with pyaoxH 2 and NEt 3 in a 1 : 1 : 2 molar ratio in MeOH afforded 2·10H 2 O·26MeOH in good yield (65%). The two compounds display a multi-decker configuration based on stacked Ni 4 layers, {Ni 4 (pyaox) 2 (pyaoxH) 2 } 2+ x (x = 3, 1·5MeOH; x = 4, 2·10H 2 O·26MeOH); each deck consists of two square planar and two octahedral Ni II centres. The number of decks observed in 1·5MeOH and 2·10H 2 O·26MeOH depends on the nature of the inorganic anion that is present in the reaction system, which provides elements of synthetic control towards new high nuclearity Ni II species. 2·10H 2 O·26MeOH is the first structurally characterized complex of any metal displaying a quadruple-decker configuration, being also the highest nuclearity metal cluster bearing pyaoxH 2 and the highest nuclearity Ni II cluster with any type of 2-pyridyl oxime. Each cluster cation displays ferromagnetic exchange between the octahedral Ni II ions resulting in a spin ground state of S = 6 for 1 and S = 8 for 2. Magnetothermal studies have been performed and discussed for both clusters.

The reactions of various copper(ii) sources with 2-acetylpyridine, (py)(me)CO, and 2-benzoylpyridine, (py)(ph)CO, under strongly basic conditions have been studied and novel ligand transformations have been discovered. Reaction of Cu(ClO4)2·6H2O and (py)(me)CO in the presence of NBu4(n)OMe (1 : 1 : 1) in CHCl3 gave a mixture of [Cu2Cl2(HLA)2](ClO4)2 (1) and [Cu2Cl2(LB)2(ClO4)2] (2), where HLA is 3-hydroxy-1,3-di(pyridin-2-yl)-butane-1-one and LB is the zwitterionic-type ligand 3-hydroxy-1-methyl-3-(pyridin-2-yl)-3H-indolizin-4-ium. The ligand HLA is formed through an aldol reaction-type mechanism, while the formation of LB takes place via an intramolecular nucleophilic attack of the remote 2-pyridyl nitrogen atom on the positive carbonyl carbon of HLA, after the transformation of the latter through deprotonation and dehydration. The Cu(II) ions in 1 are bridged by two 2.1111 HLA ligands resulting in a long Cu(II)Cu(II) distance (5.338 Å); the metal ions in 2 are triply bridged by the alkoxide oxygen atoms of the two 2.21 LB ligands and one 2.1100 perchlorato group. The absence of α-hydrogens in (py)(ph)CO leads the reactivity of this ligand in the presence of Cu(II) to different pathways. The Cu(ClO4)2·6H2O/(py)(ph)CO/NBu4(n)OMe reaction mixture in MeOH/H2O (25 : 1 v/v) gave the dinuclear cationic complex [Cu2{(py)(ph)CO}2(LC)2](ClO4)2 (3), where LC(-) is the anion of (methoxy)(phenyl)(pyridin-2-yl)methanol formed in situ via the nucleophilic addition of MeO(-) to the carbonyl carbon of (py)(ph)CO upon Cu(II) coordination. The Cu(II) ions in the cation are doubly bridged by the deprotonated oxygen atoms of the two LC(-) ligands. Replacement of Cu(ClO4)2·6H2O with Cu(NO3)2·3H2O and NBu4(n)OMe with NMe4OH and the decrease of the H2O concentration in the above reaction system yielded the tetranuclear coordination cluster [Cu4(OMe)2(NO3)4{(py)(ph)CO}2(LC)2] (4). The Cu(II) centres in this complex define a parallelogram. Two parallel sides of the parallelogram are each supported by deprotonated oxygen atoms belonging to a 2.21 LC(-) ligand and a 2.2 MeO(-) group. The metal ions that define each of the other two sides are singly bridged by an oxygen atom of a 2.210 nitrato group. No bridging exists between the Cu(II) ions that define the two diagonals of the parallelogram. Replacement of MeOH with EtOH in the reaction system that gave 4 resulted in the dinuclear complex [Cu2(NO3)2(LD)2)(EtOH)] (5), LD(-) being the anion of (ethoxy)(phenyl)(pyridin-2-yl)methanol. The Cu(II) ions are doubly bridged by the alkoxide oxygen atoms of the two 2.21 LD(-) ligands. The 1 : 1 : 1 Cu(NO3)2·3H2O/(py)(ph)CO/NMe4OH reaction system in CH3NO2 gave the dinuclear complex [Cu2(NO3)2(LE)2] (6), where LE(-) is the anion of 2-nitro-1-phenyl-1-(pyridin-2-yl)ethanol. The OH(-) ion abstracts one of the methyl hydrogens of CH3NO2, and once the carbanion (-):CH2NO2 is formed it attacks the positive (δ+) carbonyl carbon of (py)(ph)CO; as the carbanion forms the new C-C bond, the π electrons of the carbonyl group of the original ligand are transferred completely to oxygen forming the alkoxide-type ligand LE(-). The Cu(II) ions are doubly bridged by the alkoxide oxygen atoms of the two 2.21 LE(-) ligands. Simplified mechanistic views of the Cu(II)-assisted formation of the transformed ligands are proposed. Dc magnetic susceptibility studies in the 2-300 K range for the representative complexes 3-6 reveal the presence of very strong antiferromagnetic Cu(II)Cu(II) exchange interactions in the dinuclear complexes 3, 5, and 6 and within the dimeric {Cu2(OMe)(NO3){(py)(ph)CO}(LC)}(+) subunits of 4. The strong antiferromagnetic coupling is discussed in terms of the large Cu-O-Cu angles (101.0-102.9°) in the dinuclear, planar {Cu2O2} units/subunits of 3-6.