Barindra Kumar Ghosh

Synthesis, structure and magnetism of a new dicubane-like ferromagnetic tetranuclear nickel cluster containing versatile azido-only bridges and a bis(bidentate) Schiff base blocker

A new tetranuclear double-open dicubane complex [Ni4(mu 2-N3)4(mu 3-N3)2(N3)2(enbzpy)2].2H2O (enbzpy = [N,N-bis(pyridin-2-yl)benzylidene]ethane-1,2-diamine) has been characterised structurally and magnetostructurally.

Crystallographic Evidence for Reversible Symmetry Breaking in a Spin‐Crossover d7 Cobalt(II) Coordination Polymer

This work was supported by the DST and CSIR, India. J.S.C. thanks the Spanish MICINN through CTQ2009-06959 for the research fellowship “Juan de la Cierva” (18-08-463B-750). J.R. also thanks the Spanish MICINN through CTQ2009-07264.

Unexpected diversity and novel features within a family of new azide-bridged MnII complexes of pyridyl/imine ligands

A family of tetradentate ligands, [N,N′-bis(pyridine-2-yl)]ethane-1,2-diamine (L1), [N,N′-bis(pyridine-2-yl)]propane-1,3-diamine (L2) and [N,N′-bis(pyridine-2-yl)]butane-1,4-diamine (L3) has been prepared. These ligands differ only in the number of CH2 groups separating two pyridyl/imine moieties, however, in reactions with MnII and N−3 salts, they produce structurally very diverse solids; [Mn2(L1)3(N3)]n(ClO4)3n (1), [Mn2(L2)2(N3)2](PF6)2 (2) and [Mn2(L3)(N3)2]n(ClO4)2n (3). Complexes 1, 2 and 3 consist of azido-bridged magnetically dilute Mn2 pairs, arranged as 1-D, discrete and 2-D arrays, respectively. In these materials, the connection between Mn centers within the dinuclear entities occurs through mono-1,3-N−3, bis-1,3-N−3 and bis-1,1-N−3 bridges, respectively, for 1, 2 and 3. Bulk magnetic measurements reveal that the coupling within such units is antiferromagnetic (J = −1.8 cm−1, 1; J = −4.8 cm−1, 2) and ferromagnetic (J = +1.45 cm−1, 3), depending on whether the N−3 binding mode is end-to-end (EE) or end-on (EO). The reported values are given according to the convention H = −2JS1S2 for the spin-Hamiltonian.

Nitro–ruthenium(II)–arylazoimidazoles: synthesis, spectra, crystal structure and electrochemistry of dinitro-bis{1-alkyl-2-(arylazo)imidazole}ruthenium(II). Nitro–nitroso derivatives and reactivity of the electrophilic {Ru-NO}6 system

Silver ion assisted aquation of blue cis,trans,cis-RuCl2(RaaiR′)2 (4–6) leads to solvento species, blue–violet cis,trans,cis-[Ru(OH2)2(RaaiR′)2](ClO4)2 [RaaiR′ = p-R–C6H4–NN–C3H2–NN-1-R′ (1–3), abbreviated as N,N′-chelator where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1/4/7/10), CH2CH3(2/5/8/11), CH2Ph (3/6/9/12)] that have been reacted with NO2− in warm ethanol resulting violet dinitro complexes of the type, Ru(NO2)2(RaaiR′)2 (7–9). The structure in one case, [Ru(NO2)2(HaaiCH2Ph)2] (9a), has been established by X-ray diffraction as the cis-Ru(NO2)2 motif along with trans-N,N and cis-N′,N′ dispositions of the chelator N atoms around the coordination sphere. The nitrite complexes are useful synthons of electrophilic nitrosyls, and on triturating the compounds 7b–9b with conc. HClO4 nitro–nitrosyl derivatives, [Ru(NO2)(NO)(MeaaiR′)2](ClO4)2 (10b–12b), are isolated. The solution structure and stereoretentive transformation in each reaction step have been established by 1H NMR results. All the complexes exhibit strong MLCT transitions in the visible region. They are redox active and display one metal-centred oxidation and successive ligand-based reductions. The redox potentials of Ru(III)/Ru(II) (E1/2M) of 10b–12b are anodically shifted by ∼0.2 V as compared to those of dinitro precursors 7b–9b. The ν(NO) > 1900 cm−1 strongly suggests the presence of linear Ru–N–O bonding. The electrophilic behaviour of metal bound nitrosyl has been proved in one case (12b) by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group, and the heteroleptic tris-chelates thus formed are characterised.

Crystal engineering through [Hg(SCN)4]2− templates: S⋯S interaction mediated 3-D parallel interpenetration in the self-assembled superstructure of [Hg(SCN)4]2− and protonated 2,2′- dipyridylamine

An organic–inorganic hybrid solid (dpaH)2[Hg(SCN)4] (1) (dpa = 2,2′-dipyridylamine) based on an anionic template [Hg(SCN)4]2− has been designed and synthesized. X-Ray crystallographic structural analysis reveals that [Hg(SCN)4]2− templates assemble dpaH+ units into a 2-D layer structure through strong hydrogen bonding. In the 2-D assembly the [Hg(SCN)4]2− units act as nodes and the dpaH+ units as spacers, leading to a (4,4) net topology. The layers stack in ABAB fashion which is facilitated by S⋯S interactions between [Hg(SCN)4]2− units positioned on successive AA layers or BB layers that give rise to 3-D superstructure interpenetrated in a parallel manner.

A Heterometallic (NiII–CuII) Decanuclear Cluster Containing Two Distorted Cubane-like Pentanuclear Cores: Synthesis, Structure, and Magnetic Properties

A new heterometallic Ni(II)-Cu(II) decanuclear cluster, {[Ni(4)Cu(6)(μ-OH(2))(2)(dpkO(2))(8)(OAc)(4)(H(2)O)(4)]·2CH(3)OH·17H(2)O} (1), has been synthesized by self-assembly of the constituent metal ions and the precursor di-2-pyridylketone (dpk) of multinucleating ligand dpkO(2)(2-) and is structurally characterized. The cluster 1 is formed by the union of two symmetry-related distorted cubane-like pentanuclear cores. A magnetic study of 1 reveals strong antiferromagnetic interactions operating through the Ni-O-Ni pathway, which is independent of the assumption D = 0 or D ≠ 0. The pentanuclear cores are ferromagnetically coupled, as supported by density functional theory calculations.

Versatility of the azido bridging ligand in the first two examples of ferro–antiferromagnetic alternating nickel(II) chains

A one-pot reaction of Ni(ClO4)2·6H2O, N,N-dimethylethylenediamine (dmen) or 2-aminoethylpyridine (aep) and NaN3 affords the two [Ni(dmen)(µ-Na3)2]n1 and [Ni(aep)(µ-N3)2]n2 chains with unprecedented alternating end-on and end-to-end bridging loops perpendicular to one another; magnetic susceptibility measurements indicate that they are the first two ferro–antiferromagnetic alternating chains of NiII.

Synthesis and characterization of bis(2,2′-bipyridine)(camphorquinone monoximato)ruthenium(II) perchlorate monohydrate

Abstract The electrophilic addition of cis -[RuCl(NO)(bipy) 2 ] 2+ (bipy = 2,2′-bipyridine) to camphor in boiling methanol containing sodium methoxide affords the new complex [Ru(A)(bipy) 2 ] + ( 1 ) (A = anion of camphorquinone monoxime). An alternative synthesis of 1 is provided by the reaction of cis -RuCl 2 (bipy) 2 with HA. The cation is isolated as crystalline perchlorate monohydrate. The diamagnetic complex displays an intense metal-to-ligand charge-transfer transition at ca 440 nm. A reversible rutheniuim(III)-ruthenium(II) couple near 0.8 V and two diimine reductions on the negative side of SCE are observed.

Mixed-ligand chelates of osmium(II/III) 8-quinolinolates: Synthesis, characterization and redox behaviour

A group of mixed-tris chelates of osmium(III) and osmium(IV) of type [OsAQ2]0/1 + [HA = glycine (glyH), picolinic acid (PicH) and quinaldic acid (qndH); HQ = 8-quinolinol] were prepared and characterized by physicochemical, magnetic and spectroscopic methods. The complexes exhibit several spin-allowed and spin-forbidden absorption bands and shoulders in the 200–700 nm region. The new chelates are electroactive and display nearly reversible OsIV-OsIII and OsIII-OsII couples in the ca. −1.1 to +0.3 V range versus s.c.e. The stability of metal oxidation states is discussed in terms of the electrochemical results.

First examples of two ferromagnetic end-to-end cyanate bridged 1D linear coordination polymers of nickel(II) containing an unsymmetrical diamine

Two new end-to-end (EE) cyanate bridged 1D coordination polymers of Ni(II) are isolated which contain linear (180°) Ni-N-C and Ni-O-C angles in Ni-NCO-Ni bridges and show ferromagnetic (F) coupling in agreement with the reported theoretical model for linear EE bridges.