A new series of nonoxido vanadium(IV) compounds [VL2] (L = L(1)-L(3)) (1-3) have been synthesized using dithiocarbazate-based tridentate Schiff-base ligands H2L(1)-H2L(3), containing an appended phenol ring with a tert-butyl substitution at the 2-position. The compounds are characterized by X-ray diffraction analysis (1, 3), IR, UV-vis, EPR spectroscopy, and electrochemical methods. These are nonoxido V(IV) complexes that reveal a rare distorted trigonal prismatic arrangement around the "bare" vanadium centers. Concerning the ligand isomerism, the structure of 1 and 3 can be described as intermediate between mer and sym-fac isomers. DFT methods were used to predict the geometry, g and (51)V A tensors, electronic structure, and electronic absorption spectrum of compounds 1-3. Hyperfine coupling constants measured in the EPR spectra can be reproduced satisfactorily at the level of theory PBE0/VTZ, whereas the wavelength and intensity of the absorptions in the UV-vis spectra at the level CAM-B3LYP/gen, where "gen" is a general basis set obtained using 6-31+g(d) for S and 6-31g for all the other elements. The results suggest that the electronic structure of 1-3 can be described in terms of a mixing among V-dxy, V-dxz, and V-dyz orbitals in the singly occupied molecular orbital (SOMO), which causes a significant lowering of the absolute value of the (51)V hyperfine coupling constant along the x-axis. The cyclic voltammograms of these compounds in dichloroethane solution display three one-electron processes, two in the cathodic and one in the anodic potential range. Process A (E1/2 = +1.06 V) is due to the quasi-reversible V(IV/V) oxidation while process B at E1/2 = -0.085 V is due to the quasi-reversible V(IV/III) reduction, and the third one (process C) at a more negative potential E1/2 = -1.66 V is due to a ligand centered reduction, all potentials being measured vs Ag/AgCl reference.

A series of intramolecularly hydrogen-bonded zwitterionic compartmental ligands HL1-HL4, containing a pendent diamine arm that is monoprotonated and an aldehyde functionality at two different ortho-positions of a 4-halophenoxide, is reported herein. Single-crystal X-ray diffraction (SXRD) provides persuasive evidence for the identification of this class of proton-transferred zwitterions at room temperature. The solid-state photoluminescent nature of these zwitterions remains intact in aqueous and organic solutions. Grinding of HL1 and HL2 with Cu /Ni salts develop turn-on probes 1-4. Compounds 1 and 4 are dinuclear Cu and Ni species, respectively. Compound 2 is a tetranuclear Cu complex. Interestingly, compound 3 is a mononuclear Ni species in which both nitrogen atoms in the pendant diamine arm are protonated and, therefore, not coordinated to the Ni center. All these probes (1-4) display an instant response to the poison gas hydrogen cyanide (HCN) and cyanide salts present in both solid matrices and aqueous (100 % water) solution. Selective and rapid sensing of HCN gas and cyanide salts in solid/soil/water phases, without any interference, by the mechanosynthesized complexes 1-4 can be perceived easily by the naked eye under a hand-held UV lamp.

Heterobimetallic compounds [L(1)OV(V)═O→Fe(metsalophen)(H(2)O)] (1) and [L(2)OV(V)═O→Fe(metsalophen)(H(2)O)]CH(3)CN (2), where H(2)L(1) and H(2)L(2) are tridentate dithiocarbazate-based Schiff base ligands, containing a discrete V(V)-μ-O-Fe(III) angular core have been synthesized for the first time through a targeted synthesis route: confirmation in favor of such a heterobimetallic core structure has come from single-crystal X-ray diffraction analysis and electrospray ionization mass spectrometry.

Five neutral bis(μ-phenoxido)dicopper(II) complexes, [Cu 2 (L Me,Me,Me ) 2 ] ( 1 ), [Cu 2 (L Me,Me,Et ) 2 ]·CH 2 Cl 2 ( 2 ), [Cu 2 (L i -Pr, i -Pr, i -Pr ) 2 ]·2H 2 O ( 3 ), [Cu 2 (L t -Bu,Me, i -Pr ) 2 ] ( 4 ), and [Cu 2 (L t -Bu, t -Bu, i -Pr ) 2 ]·H 2 O ( 5 ) have been synthesized and characterized by single-crystal X-ray diffraction analyses, magnetic studies, and density functional theory (DFT) calculations, in which the ligands [H 2 L Me,Me,Me = N , N -bis(2-hydroxy-3,5-dimethylbenzyl)- N ′, N ′-dimethylethylene-1,2-diamine, H 2 L Me,Me,Et = N , N -bis(2-hydroxy-3,5-dimethylbenzyl)- N ′, N ′-dimethylethylene-1,2-diamine, H 2 L i -Pr, i -Pr, i -Pr = N , N -bis(2-hydroxy-3,5-diisopropylbenzyl)- N ′, N ′-diisopropylethylene-1,2-diamine, H 2 L t -Bu,Me, i -Pr = N , N -bis(2-hydroxy-3- tert -butyl-5-methylbenzyl)- N ′, N ′-diisopropylethylene-1,2-diamine, and H 2 L t -Bu, t -Bu, i -Pr = N , N -bis(2-hydroxy-3,5-di- tert -butylbenzyl)- N ′, N ′-diisopropylethylene-1,2-diamine] contain the same [O,N,N,O]-donor atoms combination but differ in substituents at phenol rings and at an amino nitrogen atom. The effect of these remote substituents on the nature of exchange coupling interactions (ferromagnetic vs antiferromagnetic) between the copper(II) ions has been investigated. The average Cu–O–Cu angle, Cu–O–Cu–O torsion angle, and Cu···Cu separation in 1–5 are varied sy...

A new family of [3 + 3] hexanuclear 3d-4f complexes [(μ-CO){CoLnL(μ-OH)(OH)}]-(ClO)·mCHOH·nHO (1-5) [Ln = La (1), Gd (2), Tb (3), Dy (4), and Ho (5)] have been prepared in moderate to high yields (62-78%) following a self-assembly reaction between the ligand 6,6',6''-(nitrilotris(methylene))tris-(2-methoxy-4-methylphenol) (HL), Co(OAc)·4HO and the lanthanide ion precursors in the mandatory presence of tetrabutylammonium hydroxide. During the reaction, atmospheric carbon dioxide is fixed in the product molecule as a bridging carbonato ligand which connects all the three lanthanide centers of this molecular assembly through a rare η:η:η-μ mode of bridging as revealed from X-ray crystallography. The metal centers in all these compounds, except the Gd analogue (2), are coupled in antiferromagnetic manner while the nature of coupling in the CoGd complex is ferromagnetic. DFT calculations revealed that this ferromagnetic interaction occurs most likely by the Co-Gd superexchange, mediated via the bridging oxygen atoms. Only the Co-Dy compound (4) displayed a slow relaxation of the magnetization at a very low temperature as established by AC susceptibility measurements. The data provides an estimation of the activation energy U/k = 9.2 K and the relaxation time constant τ = 1.0 × 10 s.