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Syntheses and characterization of mono- (1) and binuclear (2) heteroleptic Ni(II) complexes having redox active dipyrrins ligands have been described and their electrochemical hydrogen generation ability explored. Molecular structures of the complexes have been authenticated by X-ray-single crystal analyses. The electrocatalytic properties and stability of the complexes toward hydrogen evolution reactions have been investigated by cyclic voltammetric and bulk electrolysis studies at a fixed potential (−1.8 V) in an organic medium in presence of the acetic acid as a weak proton source. The probable mechanism of the electrocatalytic proton reduction reaction has also been supported by theoretical studies. [Display omitted] • The design of two new homogenous molecular catalysts for proton reduction reaction based on dipyrrin ligands. • The stability and H 2 production capability of these complexes has also been investigated by bulk electrolysis study. • We have also supported the tentative mechanism of proton reduction based on theoretical calculation. The effect of nuclearity on electrochemical hydrogen generation using new heteroleptic Ni(II) complexes containing redox-active dipyrrin and dithiocarbamate ligands has been described. Complexes 1 – 2 have been meticulously characterized by spectroscopic studies (ESI-MS, IR, 1H, 13C NMR, UV–vis) and their structures unambiguously confirmed by X-ray single crystal analyses. Electrocatalytic properties of the complexes toward hydrogen evolution reaction have been investigated by cyclic voltammetric studies in an organic medium in the presence of acetic acid as a weak proton source. Notably, complexes 1 and 2 produce H 2 via doubly reduced Ni(II) species i.e. Ni(0) in the presence of acetic acid. Further, these complexes exhibited significant electrocatalytic activity (TOF: 264 (1) and 650 s−1 (2). Controlled potential electrolysis established a minimum Faradaic efficiency of 92 (1) and 96 % (2). Complex 2 exhibited higher turnover frequency relative to 1 , while 1 showed lower overpotential (0.35 V) in comparison to 2 (0.45 V). The stability of the complexes and the amount of produced H 2 has been investigated by bulk electrolysis study. A tentative mechanism (ECEC; E, electrons and C, chemical steps) and involved intermediate species for the proton reduction reaction for 1 has been established by theoretical studies. [ABSTRACT FROM AUTHOR]

A series of copper(ii) complexes (1–9 and 3′) derived from bis-dipyrrin ligands (L1–L9 and L3′) with diverse spacer lengths [–(CH2)n–] have been described. Structural diversities in these complexes have been explicitly established by spectral and structural studies on these and a closely related nickel(ii) complex (3′′). All the ligands and complexes have been thoroughly characterized by spectroscopic studies (ESI-MS, IR, 1H, 13C NMR, UV/vis) and structures of 2, 3′, 3′′, 6, 8 and 9 were determined by X-ray single crystal analyses. It has been unambiguously established that ligands with n≤ 6 gave heteroleptic binuclear (1–5), while those with n≥ 7 yielded homoleptic mononuclear (6–9) bis-dipyrrinato complexes. Spectral and structural studies revealed distorted square planar (1–5) and distorted tetrahedral geometries (6–9) about the copper(ii) centre in these complexes which has further been evidenced by EPR and electrochemical studies. Structural differences based on the odd and even number of methylene spacers in these complexes have been supported by DFT studies. A line between the syn- and anti-conformations of the complexes has been drawn on the basis of a limiting spacer length. [ABSTRACT FROM AUTHOR]

Synthesis of four new arene ruthenium(II) complexes [(η 6 -C 10 H 14 )RuCl(MFPdpm)] ( 1 ); [(η 6 -C 12 H 18 )Ru-Cl(MFPdpm)] ( 2 ); [(η 6 -C 10 H 14 )RuCl(PFPdpm)] ( 3 ) and [(η 6 -C 12 H 18 )RuCl(PFPdpm)] ( 4 ) containing dipyrrin ligands 5-(4-fluoro)phenyldipyrromethene (MFPdpm) and 5-(penta-fluoro)phenyldipyrromethene (PFPdpm) have been described. The ligands and complexes have been thoroughly characterized by elemental analyses, spectroscopic studies (ESI-MS, IR, 1 H, 13 C NMR, UV–Vis) and structure of the representative complex 4 determined by X-ray single crystal analyses. DNA binding activities of 1 – 4 have been investigated by UV–Vis and fluorescence spectroscopy and their binding through the minor groove of DNA has been established by molecular docking studies. The complexes 1 – 4 exhibit significant cytotoxicity toward human lung cancer cell line (A549). Cytotoxicity, morphological changes, and apoptosis studies have been evaluated through MTT assay, Hoechst 33342/PI staining, and cell cycle analysis by fluorescence activated cell sorting (FACS). In vitro antitumor activity and cytotoxicity of the complexes lie in the order 4 > 3 > 2 > 1 . [ABSTRACT FROM AUTHOR]

Synthesis of 2-chloro-3-(di(1H-pyrrol-2-yl)methyl)quinoline (L) and their Ru(II) complexes (R1-R2) have been described. Characterization of the ligands and complexes have been achieved by spectral studies (IR, 1H, 13C, ESI–MS, electronic absorption,) and crystal structures of R1 determined crystallographically. Interaction of the complexes with calf thymus DNA (CT DNA) has been supported by absorption titration studies and ethidium bromide experiments. [Display omitted] • Ru(II)-arene complexes. • DNA/protein interactions. • Anticancer activity. • DFT calculations. Arene ruthenium complexes [(η 6–arene)Ru(L)Cl] (η 6–arene = benzene, R1 ; p -cymene, R2) containing the chelating ligand (2–chloro–3–(di(1H–pyrrol–2–yl)methyl)quinoline) (L) have been synthesized and carefully characterized by various studies (1H and 13C NMR, IR, ESI–MS, UV–vis). The structure of R1 has been verified by X-ray single crystal analyses. Binding of the complexes with calf thymus DNA (CT–DNA) has been investigated by absorption titration, ethidium bromide (EB) displacement and viscosity measurements. Experimental binding constants (5.1 × 104 M−1, R1 ; 5.7 × 104 M−1, R2) suggested appreciable bonding of the complexes with CT–DNA. Fluorescence, synchronous and 3D fluorescence spectroscopic studies showed that complexes strongly bind with bovine serum albumin. Intercalative interaction of the complexes with DNA has been further supported by DFT studies. Our studies have shown potential anticancer activity of both the complexes R1 and R2 against T cell lymphoma. Among these complexes R2 showed better anticancer activity relative to R1 (IC 50 , R1, 30 μM and R2, 20 μM). [ABSTRACT FROM AUTHOR]