Anik Bhattacharyya

A combined experimental and computational study of supramolecular assemblies in ternary copper(II) complexes with a tetradentate N-4 donor Schiff base and halides

Three new copper(II) complexes, [Cu(L)(Cl)]ClO4 (1), [Cu(L)(Br)]ClO4 (2) and [Cu(L)(I)]ClO4 (3), have been prepared from a tetradentate symmetrical Schiff base, N,N′-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L), and characterized by elemental analysis, IR and UV-Vis spectroscopy and single-crystal X-ray diffraction studies. Extended supra-molecular networks were generated through different weak non-covalent forces. Density functional theory (DFT) calculations were employed to estimate the contribution of each interaction in the formation of the assembly using several theoretical models. The interplay between the anion–π and π–π interactions is also analyzed and a mutual reinforcement of both interactions is demonstrated. The assignment of the contribution of each interaction and its mutual influence is certainly important to shed light on the delicate mechanism that governs the molecular recognition and crystal packing.

Spontaneous resolution of P and M helical copper(II) MOFs built from achiral precursors

Two enantiomorphic (P and M) helical coordination polymers of [Cu(μ1,3-N3)(L)]n {HL = 2-(dimethylamino)ethyliminomethylnaphthalen-2-ol} have been synthesized by the self-assembly of the achiral precursors via spontaneous resolution. The structures have been confirmed by single crystal X-ray crystallography. Solid-state circular dichroism spectra have confirmed the chirality of both P and M helical chains.

Field-induced ferromagnetism due to magneto-striction in 1-D helical chains

Two homochiral copper(II) helices, [Cu(μ1,3-N3)(L1)]n (1) and [Cu(μ1,3-NCO)(L2)]n (2), with end-to-end pseudohalide bridges, were synthesized using two N2O donor achiral Schiff bases via spontaneous chiral resolution. Field-induced ferromagnetic ordering due to magneto-striction in homochiral 1-D helix [Cu(μ1,3-N3)(L1)]n (1) is reported for the first time. At temperatures below 5.5 K, under a magnetic field of 1 T, orthogonality between the magnetic orbitals of copper centres increases significantly due to the contraction of lattice parameters, giving rise to long-range ferromagnetic ordering in the helical chain. The magneto-dielectric results are also indicative of the observed magneto-striction effect in the present complex 1. We believe that this study will uncover a new way to invoke long-range ferromagnetic ordering in 1-D helical chains.

Both end-on and end-to-end azide bridged tetranuclear ferromagnetic nickel(II) Schiff base complexes

Variable temperature magnetic measurements of a novel tetranuclear nickel(II) complex, consisting of two pseudo-dinuclear entities bridged by an end-to-end azide, indicate the presence of both intra- and inter-dinuclear ferromagnetic interactions (J1 = 16.48 cm−1 and J2 = 24.17 cm−1, respectively), as also corroborated by DFT calculations (J1 = 12.0 cm−1 and J2 = 29.2 cm−1).