Soumen Mistri

A rare supramolecular assembly involving ion pairs of coordination complexes with a host–guest relationship: synthesis, crystal structure, photoluminescence and thermal study

A two component new coordination complex having formula {[Mn(phen)2Cl(H2O)]+ [Mn(phen)(btc)(H2O)3]−(CH3OH)·2(H2O)} (1) [btc = 1,3,5-benzenetricarboxylate trianion; phen = 1,10-phenanthroline] has been synthesized and characterized by X-ray single crystal structure, which reveals that one of the components is positively charge and the other is negatively charged. Complex 1 is a rare example of a coordination complex consisting of coordination ion pairs. The btc containing anionic subunits give rise to a 3D supramolecular host based on a coordination driven hydrogen bonding synthon. Cationic subunits occupy the 1D channels of the anionic supramolecular host.

Synthesis, characterization, TDDFT calculation and biological activity of tetradentate ligand based square pyramidal Cu(II) complexes

Distorted square pyramidal complexes [Cu(L1)(H2O)]·ClO4 (1), [Cu(L2)(H2O)]·ClO4 (2) and [Cu(L3)(H2O)]·ClO4 (3) (HL1 = o-{[2-(2-aminoethylamino)ethylimino]methyl}phenol; HL2 = 2-{[2-(2-aminoethylamino)ethylimino]methyl}-6-methoxyphenol; HL3 = o-{1-[2-(2-aminoethylamino)ethylimino]ethyl}phenol) have been synthesized, and characterized by X-ray crystallography and spectroscopic analysis. All the complexes exhibit fluorescence at room temperature [λex = 267 nm, λem = 312, 329 and 357 nm, φ = 0.52 for 1; λex = 272 nm, λem = 312, 329 and 355 nm, φ = 0.46 for 2; λex = 265 nm, λem = 312, 356 and 377 nm, φ = 0.33 for 3]. The electronic structure and photophysical properties of the ligands and complexes were calculated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods using the B3LYP, B3PW91 and MPW1PW91 functionals, with 6-31G (d-p) and LanL2DZ basis sets. The results of TD-DFT calculations are functional-dependent and among the functionals, B3LYP was able to best reproduce the experimental results. Catecholase activity of 1–3 has been investigated using 3,5-di-tert butyl catechol (3,5-DTBC) as the model substrate and found that complexes are active for catalyzing the aerobic oxidation of 3,5-DTBC to 3,5-di-tert butyl benzoquinone (3,5-DTBQ). The compound with more distorted square pyramidal geometry shows a higher rate of catalytic activity. All the complexes have been tested for their anticancer activities in human breast (MCF7) cancer cell lines. Complexes show dose dependent suppression of cell viability with IC50 values 30, 68 and >100 μM for 1, 2 and 3, respectively. Anticancer activities of 1–3 and cisplatin were compared, and found that 1–3 were relatively less active than cisplatin.

The supramolecular assembly of tetraaqua-(pyridine-2,5-dicarboxylato)- copper(II) complex: Crystal structure, TD-DFT approach, electronic spectra, and photoluminescence study

The copper(II) complex, {[Cu(2,5-pdc)(H2O)4]·H2O} (1) [2,5-pdc = pyridine-2,5-dicarboxylate], has been synthesized and characterized by elemental analysis, IR spectroscopy, and X-ray crystallography. The metal shows a distorted octahedral coordination sphere and in solid state the complex forms a 3-D supramolecular network via hydrogen bonding and off-center anti-parallel π–π stacking interactions between py rings. At room temperature, 1 exhibits fluorescence in methanolic solution [λex = 226 nm, λem = 309, 330, and 341 nm]. The geometry optimization at the B3LYP/LanL2DZ level led to a five-coordinate copper having a distorted square pyramidal geometry. The electronic spectrum of this compound is compared with the results obtained by employing density functional theory (DFT) and time dependent density functional theory calculations. Graphical Abstract

Synthesis, crystal structure, DFT/TDDFT calculation, photophysical properties and DNA binding studies of morpholino moiety ligand based two Cu(II) complexes in combination with carboxylates

The complexes [Cu(L)(pa)] (1) and [Cu(L)(mb)] (2) (HL = o-{(3-morpholinopropylimino)methyl}phenol; pa = 3-phenylacrylate; mb = p-methylbenzoate) have been synthesized and characterized by elemental analysis, single crystal X-ray crystallography, FT-IR, UV-vis electronic absorption spectroscopic analysis. Complexes 1 and 2 are mononuclear with distorted square pyramidal geometries where the Schiff base coordinates to copper(II) in the tridentate (O, N, N) chelating mode. These three atoms plus one carboxylate oxygen define the equatorial plane of the square pyramid while the axial position is occupied by carboxylate oxygen at a relatively longer distance. Weak C–H⋯π interactions result the formation of 2D supramolecular structures for both complexes. At room temperature complexes 1 and 2, exhibit fluorescence with a quantum yield (Φs) of 0.129 and 0.117, respectively. The UV-vis electronic absorption and IR spectral data of complexes have been compared with the results obtained by employing DFT and time dependent density functional theory (TD-DFT) calculation using the B3LYP, B3PW91 and MPW1PW91 functionals, with LanL2DZ basis set. The results of these calculations are functional-dependent and among the functionals, B3LYP proved to better reproduce the experimental results. The interactions of complexes with the calf thymus DNA (CT-DNA) were investigated using electronic absorption and fluorescence spectroscopic techniques. The studies reveal that the binding affinities of complexes 1 and 2 with CT-DNA are in the order of 1.68 × 105 M−1 and 2.271 × 105 M−1, respectively. A study of the effect of various metal ions on the electronic absorption and fluorescence spectra of HL reveals that it selectively senses the Cu(II) ions.

Manganese(IV) complex with a polydentate Schiff base ligand: synthesis, crystal structure, TDDFT calculation, electronic absorption and EPR spectral study

Abstract A six-coordinate Mn(IV) complex, [Mn(H2L)2] (1) [H4L = 2-methoxy-6-(tris(hydroxymethyl)methyliminomethyl)phenol], was synthesized and characterized by elemental analysis, single-crystal X-ray crystallography, FTIR, UV–Vis electronic absorption, and EPR spectroscopy. The single-crystal structural determination reveals that the complex crystallizes in tetragonal space group P41212 and the tridentate Schiff base ligands are arranged in mer configuration chelating manganese, which exhibits as slightly distorted octahedral coordination sphere with a N2O4 chromophore. Weak hydrogen bonding interactions of uncoordinated hydroxyl groups result in a 2-D supramolecular structure. The UV–Vis electronic absorption and IR spectral data of 1 have been compared with the results obtained by employing DFT and time-dependent density functional theory calculation using B3LYP, B3PW91, and MPW1PW91 functionals, with 6-31G (d-p) and LanL2MB basis sets. The results of these calculations are functional-dependent and, among those used, B3PW91 proved to better reproduce the experimental results.