3 )] (6). Structural characterization of these compounds 4-6 were accomplished by using various physico-chemical techniques. Single crystal X-ray diffraction data of complexes 4 and 5 proved their distorted square planar geometry. In order to ascertain the potential of the above synthesised compounds towards biomolecular interactions, additional experiments involving interaction with calf thymus DNA (CT DNA) and bovine serum albumin (BSA) were carried out. All the ligands and corresponding nickel(II) chelates have been screened for their scavenging effect towards O 2 − , OH and NO radicals. The efficiency of complexes 4-6 to arrest the growth of HeLa, HepG-2 and A431 tumour cell lines has been studied along with the cell viability test against the non-cancerous NIH 3T3 cells under in vitro conditions.

Structural characterization of complexes 5-8 were accomplished by using various physico-chemical techniques. In order to study the influence of substitution in the ligand and its planarity on the biological activity of complexes 5-8 containing them, suitable hydrazone ligands 1-4 have been selected in this study. Single crystal diffraction data of complexes 5, 7 and 8 proved the geometry of the complexes to be distorted square planar with a 1 : 1 ratio between the metal ion and the coordinated hydrazones. To provide more insight on the mode of action of complexes 5-8 under biological conditions, additional experiments involving their interaction with calf thymus DNA (CT DNA) and bovine serum albumin (BSA) were monitored by UV-visible and fluorescence titrations respectively. Further, the ligands 1-4 and corresponding nickel(II) chelates 5-8 have been tested for their scavenging effect towards OH and O 2 -radicals. The effect of complexes 5-8 to arrest the growth of HeLa and Hep-2 tumour cell lines has been studied along with the cell viability against the non-cancerous NIH 3T3 cells under in vitro conditions.

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A new series of geometrically different complexes containing ferrocenyl hydrazone ligands were synthesised by reacting suitable precursor complex [MCl 2 (PPh 3 ) 2 ] with the ligands HL 1 or HL 2 (where M = Cu(II) or Ni(II); HL(5) and [Ni(L 2 ) 2 ] (6) were characterised by various spectral studies. Among them, complexes 3 and 5 characterised by single crystal X-ray diffraction showed a distorted tetrahedral structure for the former with 1 : 1 metal-ligand stoichiometry, but a distorted square planar geometry with 1 : 2 metal-ligand stoichiometry in the case of the latter. Systematic biological investigations like DNA binding, DNA cleavage, protein binding, free radical scavenging and cytotoxicity activities were carried out using all the synthesised compounds and the results obtained were explained on the basis of structure-activity relationships. The binding constant (K b ) values of the synthesised compounds are found to be in the order of magnitude 10 3 -10 5 M −1 and also they exhibit significant cleavage of supercoiled (SC) pUC19 DNA in the presence of H 2 O 2 as co-oxidant. The conformational changes of bovine serum albumin (BSA) upon binding with the above complexes were also studied. In addition, concentration dependent free radical scavenging potential of all the synthesised compounds (1-6) was also carried out under in vitro conditions. Assays on the cytotoxicity of the above complexes against HeLa and A431 tumor cells and NIH 3T3 normal cells were also carried out. † Electronic supplementary information (ESI) available: Crystal packing diagram of the unit cell of complexes 3 and 5 (Fig. S1 and S2), Electronic absorption spectra of binding of ligands 1 and 2 with DNA (Fig. S3), Electronic absorption spectra of binding of complexes 3, 4 and 5 with DNA (Fig. S4 and S5), Circular dichroism spectra of DNA and ligands 1 and 2 (Fig. S6), Circular dichroism spectra of DNA and complexes 3, 4 (Fig. S7), Emission spectra of binding of complexes 3, 4 and 5 with BSA (Fig. S8 and S9), Synchronous spectra (Δλ = 15 and 60 nm) of binding of complexes 3, 4 and 5 with BSA (Fig. S10, S11 and S12). CCDC reference numbers 796259 and 822888 for complexes 3 and 5.

Two new copper(I) hydrazone complexes have been synthesised from bivalent copper precursor [CuCl(2)(PPh(3))(2)] and ferrocene containing bidentate hydrazone ligands HL(1) (1) or HL(2) (2). Based on the elemental analyses and spectroscopic data, the complexes are best formulated as [CuL(1)(PPh(3))(2)] (3) and [CuL(2)(PPh(3))(2)] (4) of the monovalent copper ion. Solid state structures of ligand 2 and its corresponding complex 4 were also determined. The DNA/albumin interactions of all the synthesised compounds were investigated using absorption, emission and synchronous fluorescence studies. Further, antioxidant properties of all the compounds have also been checked against ABTS, O(2)(-) and OH radicals. Additionally, the in vitro cytotoxic activity of compounds 1-4 was assessed using tumour (HeLa, A431) and non-tumour (NIH 3T3) cell lines.

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The condensation reactions of 2-formylindole (1) or 2-formylphenanthro[9,10-c]pyrrole (2) with various aromatic amines afforded the corresponding phenyl or phenanthrene ring fused mono-/bis-iminopyrrole ligand precursors 3-8, which, upon reaction with BPh in an appropriate molar ratio, led to the new mono- and diboron chelate compounds PhB[NCHC(H)[double bond, length as m-dash]N-2,6-Ar] (Ar = 2,6-iPrCH9; CH10), PhB[(NCHC(H)[double bond, length as m-dash]N)-1,4-CH]BPh11, PhB(NCHC(H)[double bond, length as m-dash]N-Ar) (Ar = 2,6-iPrCH12; CH13), and PhB[(NCHC(H)[double bond, length as m-dash]N)-1,4-CH]BPh14, respectively. Boron complexes 12-14, containing a phenanthrene fragment fused to the pyrrolyl C3-C4 bond, are highly fluorescent in solution, with quantum efficiencies of 37%, 61% and 58% (in THF), respectively, their emission colours ranging from blue to orange depending on the extension of π-conjugation. Complexes 9-11, containing a benzene fragment fused to the pyrrolyl C4-C5 bond, are much weaker emitters, exhibiting quantum efficiencies of 10%, 7% and 6%, respectively. DFT and TDDFT calculations showed that 2,6-iPrCHN-substituents or, to a smaller extent, the indolyl group prevent a planar geometry of the ligand in the excited state and reveal the existence of a low energy weak band in all the indolyl complexes, which is responsible for the different optical properties. Non-doped single-layer light-emitting diodes (OLEDs) were fabricated with complexes 9-14, deposited by spin coating, that of complex 13 revealing a maximum luminance of 198 cd m.