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Two mononuclear fluorophore-labeled copper(II) complexes [Cu(nip)(acac)](+)(2) and [Cu(nip)2](2+) (3), where fluorophore is 2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (nip) (1) and acac is acetylacetone, have been synthesized and characterized by various techniques. The ligand 1 and complex 2 are structurally characterized by single-crystal X-ray diffraction. The coordination geometries around the copper are square planar in solid as well as solution state as evidenced by electron paramagnetic resonance (EPR) spectroscopy. The density functional calculations carried out on 1-3 have shown that electron-rich regions in the highest occupied orbital are localized on the naphthalene and partly on the phenanthroline moiety. Both complexes 2 and 3 in dimethyl sulfoxide (DMSO) exhibit near square planar structure around the metal ion in their ground state. Time-dependent density functional theory (TD-DFT) calculations reveal that Cu(II) ion in complex 2 shows tetrahedral coordination around the metal while 3 retains its square planar geometry in the lowest excited state. The interaction of complexes with calf-thymus DNA (CT DNA) has been explored by using absorption, emission, thermal denaturation, and viscosity studies, and the intercalating mode of DNA binding has been proposed. The complexes cleave DNA oxidatively without any exogenous additives. The protein binding ability has been monitored by quenching of tryptophan emission in the presence of complexes using bovine serum albumin (BSA) as model protein. The compounds showed dynamic quenching behavior. Further, the anticancer activity of the complexes on MCF-7 (human breast cancer), HeLa (human cervical cancer), HL-60 (human promyelocytic leukemia), and MCF-12A (normal epithelial) cell lines has been studied. It has been observed that 3 exhibits higher cytotoxicity than 2, and the cells undergo apoptotic cell death.

Electronic structure and molecular electrostatic potential (MESP) in ferrocene (FC), cucurbit[n]urils (CB[n]) with n = 5-8, and their host-guest complexes are obtained within the framework of density functional theory. MESP topography that is employed to gauge the dimensions of the CB[n] cavity estimates that the cavity height increases from 7.25 to 7.70 A along CB[n] homologue series, whereas the diameter of the CB[8] (8.57 A) cavity is larger than twice that of CB[5] (3.91 A). MESP investigations reveal deeper minima near ureido oxygens in CB[5] along with large electron-rich regions at its portal. A lateral interaction of the guest FC with hydrophilic exterior of the CB[n] portal and its encapsulation within hydrophobic cavity of the host are analyzed. The present calculations suggest that CB[5] does not yield stable complexes in either case. FC interacts laterally with CB[6], and inclusion of the guest occurs, both parallel as well as perpendicular to the CB[n] axis, in the cavity of higher homologue. Self-consistent reaction field studies indicate that, in the presence of water as a solvent, encapsulation of FC in parallel fashion is favored within CB[7] and CB[8] cavities. NMR chemical shifts (delta(H)) of CB[n] protons remain practically unchanged with an increase in the cavity size; however, they are influenced significantly by water. The spectra thus obtained in aqueous solution agree with those observed experimentally. The delta(H) values in FC-CB[n] complexes indicate deshielding of FC protons directed toward portals, while those pointing toward nitrogens exhibit up-shifts in the spectra.

The cation coordination of the bis(trifluoromethanesulfone)imide (TFSI) anion (CF3SO2)2N- has been studied using the molecular electrostatic potential (MESP) topography as a tool. The critical points of MESP are employed for searching the cation binding sites of the anion. Subsequent ab initio Hartree−Fock calculations using the 6-31G(d) basis for the Li+TFSI- ion pair engenders seven local minima on the potential energy surface of the complex. In the lowest energy conformer, Li+ coordinates with two oxygens, one from each of the different SO2 groups on the central nitrogen, with the anion having C 2 point group symmetry. Li+TFSI- conformers with the cation in coordination (a) with oxygen and nitrogen atoms of the anion or (b) with the two oxygens of the same SO2 group as well as (c) with the oxygen and one of the fluorines at the CF3 end, typically 48−114 kJ mol-1 higher in energy than the lowest minimum, have also been obtained. The SNS bond angle in the free anion as well as that in the Li+TFSI- ion pair turns out to be in the range 126°−132°, which agrees well with the X-ray data on the crystal hydrate structure for the HTFSI. A comparison of the vibrational spectra of the free TFSI anion and the Li+TFSI- ion pair conformers reveals that the S−N stretching vibration at 815 cm-1 can be used as a probe to distinguish the different ion pair conformers. A near doublet at the 703 cm-1 in the C 2 symmetry of the TFSI anion on coordination shows a separation of 7−60 cm-1 in the ion pair.

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