Rampal Pandey

DNA Binding and Anti-Cancer Activity of Redox-Active Heteroleptic Piano-Stool Ru(II), Rh(III), and Ir(III) Complexes Containing 4-(2-Methoxypyridyl)phenyldipyrromethene

The synthesis of four novel heteroleptic dipyrrinato complexes [(η(6)-arene)RuCl(2-pcdpm)] (η(6)-arene = C6H6, 1; C10H14, 2) and [(η(5)-C5Me5)MCl(2-pcdpm)] (M = Rh, 3; Ir, 4) containing a new chelating ligand 4-(2-methoxypyridyl)-phenyldipyrromethene (2-pcdpm) have been described. The complexes 1-4 have been fully characterized by various physicochemical techniques, namely, elemental analyses, spectral (ESI-MS, IR, (1)H, (13)C NMR, UV/vis) and electrochemical studies (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)). Structures of 3 and 4 have been determined crystallographically. In vitro antiproliferative and cytotoxic activity of these complexes has been evaluated by trypan blue exclusion assay, cell morphology, apoptosis, acridine orange/ethidium bromide (AO/EtBr) fluorescence staining, and DNA fragmentation assay in Dalton lymphoma (DL) cell lines. Interaction of 1-4 with calf thymus DNA (CT DNA) has also been supported by absorption titration and electrochemical studies. Our results suggest that in vitro antitumor activity of 1-4 lies in the order 2 > 1 > 4 > 3.

DNA/Protein Binding, Molecular Docking, and in Vitro Anticancer Activity of Some Thioether-Dipyrrinato Complexes

Syntheses and characterizations of the arene ruthenium [(η(6)-C6H6)RuCl(4-mtdpm)] (1), [(η(6)-p-MeC6H4Pr(i))RuCl(4-mtdpm)] (2), and structurally analogous rhodium/iridium complexes [(η(5)-C5Me5)RhCl(4-mtdpm)] (3) and [(η(5)-C5Me5)IrCl(4-mtdpm)] (4) [4-mtdpm = 5-(4-methylthiophenyl)dipyrromethene] have been reported. Their identities have been established by satisfactory elemental analyses, electrospray ionization-mass spectrometry (ESI-MS), FT-IR, NMR ((1)H, (13)C), UV/vis, emission spectral, and electrochemical studies. Structure of the representative complex 3 has been authenticated by X-ray single crystal analyses. The complexes 1-4 effectively bind with calf thymus DNA (CT DNA) through intercalative/electrostatic interactions. In addition, these exhibit significant cytotoxicity toward Dalton lymphoma (DL) cell line and cause static quenching of the bovine serum albumin (BSA) fluorophore. The antiproliferative activity, morphological changes, and apoptosis have been evaluated by MTT assay, acridine orange/ethidium bromide (AO/EtBr) fluorescence staining, and DNA ladder assay. Mode of interaction of the complexes with DNA/protein has also been supported by molecular docking. Various studies revealed remarkable decrease in the in vitro DL cell proliferation and induction of the apoptosis by 1-4, which lies in the order 2 > 1 > 4 > 3.

Heteroleptic Dipyrrinato Complexes Containing 5-Ferrocenyldipyrromethene and Dithiocarbamates as Coligands: Selective Chromogenic and Redox Probes

Six heteroleptic dipyrrinato complexes [Ni(fcdpm)(dedtc)] (1), [Ni(fcdpm)(dipdtc)] (2), [Ni(fcdpm)(dbdtc)] (3), [Pd(fcdpm)(dedtc)] (4), [Pd(fcdpm)(dipdtc)] (5), and [Pd(fcdpm)(dbdtc)] (6) (fcdpm = 5-ferrocenyldipyrromethene; dedtc = diethyldithiocarbamate; dipdtc = diisopropyldithiocarbamate; dbdtc = dibutyldithiocarbamate) have been synthesized and characterized by elemental analyses and spectral (ESI-MS, IR, (1)H, (13)C NMR, UV-vis) and electrochemical studies. Crystal structures of 1, 2, 4, and 5 have been authenticated by X-ray single-crystal analyses. Nickel-based complexes 1-3 display selective chromogenic and redox sensing for Hg(2+) and Pb(2+) ions, while palladium complexes 4-6 display selective chromogenic and redox sensing only for Hg(2+). Electronic absorption, ESI-MS, and electrochemical studies indicated that sensing arises from interaction between 1-3 and Hg(2+)/Pb(2+) through sulfur of the coordinated dithiocarbamates, while it arises from the pyrrolic nitrogen of fcdpm and dithiocarbamate sulfur from 4-6 and Hg(2+). Different modes of binding between Ni and Pd complexes have further been supported by theoretical studies. The receptor-cation binding constants (K(a)) and stoichiometry between probes and Hg(2+)/Pb(2+) have been estimated by the Benesi-Hildebrand method and Jobs plot analysis. Detection limits for 1-3 toward Hg(2+)/Pb(2+) and 4-6 for Hg(2+) have been found to be reasonably high.

A schiff base and its copper(II) complex as a highly selective chemodosimeter for mercury(II) involving preferential hydrolysis of aldimine over an ester group

The syntheses of a new Schiff base, diethyl-5-(2-hydroxybenzylidene)aminoisophthalate (HL), and a copper complex, [Cu(L2)] (1), imparting L(-), have been described. Both the ligand HL and complex 1 have been thoroughly characterized by elemental analyses, electrospray ionization mass spectrometry, FT-IR, NMR ((1)H and (13)C), electronic absorption, and emission spectral studies and their structures determined by X-ray single-crystal analyses. Distinctive chemodosimetric behavior of HL and 1 toward Hg(2+) has been established by UV/vis, emission, and mass spectral studies. Comparative studies further revealed that the chemodosimetric response solely originates from selective hydrolysis of the aldimine moiety over the ester group and 1 exhibited greater selectivity toward Hg(2+) relative to HL while the sensitivity order is reversed. Further, these followed different hydrolytic pathways but ended up with the same product analyzed for diethyl-5-aminoisophthalate (DEA). Hg(2+)-induced displacement of Cu(2+) and subsequent hydrolysis of the -HC═N- moiety in 1 affirmed the identity of the actual species undergoing hydrolysis as HL. The occurrence of Cu(2+) displacement and Hg(2+) detection via hydrolytic transformation has been supported by various physicochemical studies.

Pyridylphenyl appended imidazoquinazoline based ratiometric fluorescence “turn on” chemosensor for Hg2+ and Al3+ in aqueous media

A highly fluorescent and efficient ratiometric ‘turn on’ probe for Hg2+ and Al3+ based on quinazoline (1) has been designed and synthesized. Limit of detection (LOD) and association constants revealed its superior binding affinity and sensitivity toward Hg2+ over Al3+. Interference studies signified displacement of the complexed Al3+ by Hg2+ which has been supported by various studies.

A reusable multichannel anthraimidazoledione-based receptor for Hg2+ and Cu2+ ions: ultrasensitive, economical and facile detection of Hg2+ in real water sources through fluorescence readout

A reusable multichannel anthraimidazoledione-based receptor 1 has been developed for the highly selective detection of Cu2+ and Hg2+ in aqueous media. Based on its high fluorescence sensitivity for Hg2+, 1 was probed for the practical detection of Hg2+ in various drinking water sources wherein the trace amount of Hg2+ was detected through fluorescence ‘turn-off’ signalling. Hence, 1 revealed qualitative and quantitative practical detection of HTMs (especially Hg2+) in a competitive environment through a multichannel signaling response.

A uniquely fabricated Cu(II)-metallacycle as a reusable highly sensitive dual-channel and practically functional metalloreceptor for Fe3+ and Ca2+ ions: an inorganic site of cation detection

The present study deals with the formation of cyanuric chloride·1,2-di(pyridin-2-yl)disulfane 1 co-crystal and trimethylcyanuric acid 2 through unusual reactions of cyanuric chloride (CC). Reaction of co-crystal 1 with Co(II) and Cu(II) led to the formation of di(pyridin-2-yl)sulfane 1′ through a desulfurization reaction and complexes [Co(1′)Cl2] (3) and [Cu(1′)2-(μ2-SO4)2(H2O)2] (4). The structures of 1–4 were verified using X-ray single crystal analysis. The Cu(II)-metallacycle 4 acts as a dual-channel metalloreceptor for Fe3+ and Ca2+ through a fluorescence ‘turn-on’ response for Ca2+, a ‘turn-off’ response for Fe3+, and changes in cyclic voltammograms in pure aqueous-buffer medium (1.0 M Tris–HCl, pH 7.4). The limits of detection (LOD) for Fe3+ and Ca2+ were estimated to be 30 ppb and 0.2 ppm, respectively. For the first time, the EPR technique was applied to detect a paramagnetic ion (Fe3+) using a paramagnetic probe (4), which exhibited considerable change upon interaction with Fe3+. Further, structural elucidation of 4, use of Co(II)-complex 3 as a model compound, and FTIR and mass spectral studies suggested that the detection of cations by Cu(II)-metallacycle 4 occurs through its unique inorganic detection site (six oxygen atoms from sulphate and water groups). Due to its higher selectivity of Fe3+ over Ca2+ and other metal ions as well as its LOD for Fe3+, which is lower than the US Environmental Protection Agency permitted maximum level in drinking water (5.4 μmol L−1), 4 was successfully used for practical detection of Fe3+ in environmental water samples. The exceptionality of this report comprises the detection of vital cations using a binuclear Cu(II) metallacycle probe, utilizing the EPR technique, binding through an inorganic site and the practical application of 4 toward Fe3+ sensing.

CCDC 831542: Experimental Crystal Structure Determination

Related Article: R.Pandey, R.K.Gupta, Pei-Zhou Li, Qiang Xu, A.Misra, D.S.Pandey|2012|Org.Lett.|14|592|doi:10.1021/ol2032043