title: Cu(I) and Pb(II) complexes containing new tris(7-naphthyridyl)methane derivatives: synthesis, structures, spectroscopy and geometric conversion.
abstract: Two novel facial-capping tris-naphthyridyl compounds, 2-chloro-5-methyl-7-((2,4-dimethyl-1,8-naphthyridin-7(1H)-ylidene)(2,4-dimethyl-1,8-naphthyridin-7-yl))methyl-1,8-naphthyridine (L(1)) and 2-chloro-7-((2-methyl-1,8-naphthyridin-7(1H)-ylidene)(2-methyl-1,8-naphthyridin-7-yl))methyl-1,8-naphthyridine (L(2)), as well as their Cu(i) and Pb(ii) complexes, [CuL(a)(PPh(3))]BF(4) (1) (PPh(3) = triphenylphosphine, L(a) = bis(2,4-dimethyl-1,8-naphthyridin-7-yl)(2-chloro-5-methyl-1,8-naphthyridin-7-yl)methane), [CuL(b)(PPh(3))]BF(4) (2) (L(b) = bis(2-methyl-1,8-naphthyridin-7-yl)(2-chloro-1,8-naphthyridin-7-yl)methane), [Pb(OL(a))(NO(3))(2)] (3) (OL(a) = bis(2,4-dimethyl-1,8-naphthyridin-7-yl)(2-chloro-5-methyl-1,8-naphthyridin-7-yl)methanol) and [Pb(L(b))(2)][Pb(CH(3)OH)(NO(3))(4)] (4), have been synthesized and characterized by X-ray diffraction analysis, MS, NMR and elemental analysis. The structural investigations revealed that the transfer of the H-atom at the central carbon to an adjacent naphthyridine-N atom affords L(1) and L(2) possessing large conjugated architectures, and the central carbon atoms adopt the sp(2) hybridized bonding mode. The reversible hydrogen transfer and a geometric configuration conversion from sp(2) to sp(3) of the central carbon atom were observed when Pb(II) and Cu(I) were coordinated to L(1) or L(2). The molecular energy changes accompanying the hydrogen migration and titration of H(+) to different receptor-N at L(1) were calculated by density functional theory (DFT) at the SCRF-B3LYP/6-311++G(d,p) level in a CH(2)Cl(2) solution, and the observed lowest-energy absorption and emission for L(1) and L(2) can be tentatively assigned to an intramolecular charge transfer (ICT) transition in nature.
authors.affiliation: College of Chemistry and Chemical Engineering, Yunnan Normal University, Kunming, 650092, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Gan
authors.forename: Shao-Ming
authors.initials: SM
authors.lastname: Chi
authors.forename: Wei-Hua
authors.initials: WH
authors.lastname: Mu
authors.forename: Jia-Can
authors.initials: JC
authors.lastname: Yao
authors.forename: Li
authors.initials: L
authors.lastname: Quan
authors.forename: Cong
authors.initials: C
authors.lastname: Li
authors.forename: Zhao-Yong
authors.initials: ZY
authors.lastname: Bian
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Wen-Fu
authors.initials: WF
authors.lastname: Fu