title: Synthesis, characterization, photoinduced isomerization, and spectroscopic properties of vinyl-1,8-naphthyridine derivatives and their copper(I) complexes.
abstract: A series of 1,8-naphthyridine derivatives containing vinyl, 2-(2-acetylamino-pyridine-6-ethylene)-4-methyl-7-acetylamino-1,8-naphthyridine (L(1)), 2-(2-acetylamino-pyridine-6-ethylene)-1,8-naphthyridine (L(2)), 2-(2-acetylamino-pyridinyl-6-ethylene)-4-methyl-7-hydroxyl-1,8-naphthyridine (L(3)), 2-(2-diacetylamino-pyridinyl-3-ethylene)-7-diacetylamino-1,8-naphthyridine (L(4)), and 7-(2-diacetylamino-pyridinyl-3-ethylene)-4'-acetyl-pyrrolo[1',5'-a]-1,8-naphthyridine (L(5)), as well as complexes [CuL(1)(PCy(3))](BF(4))(2) (1) (PCy(3) = tricyclohexylphosphine), [Cu(2)L(1)(PPh(3))(4)](BF(4))(2) (2) (PPh(3) = triphenylphosphine), [Cu(2)L(1)(dppm)](BF(4))(2) (3) (dppm = bis(diphenylphosphino)methane), and [Cu(2)(L(1))(dcpm)][BF(4)](2) (4) (dcpm = bis(dicyclohexylphosphino)methane, were synthesized. All these compounds, except for L(1) and L(2), were characterized by single crystal X-ray diffraction analysis, and a comprehensive study of their spectroscopic properties involving experimental theoretical studies is presented. We found an intramolecular 1,3-hydrogen transfer during the formation of L(3) and L(4), which in the case of the latter plays an important role in the 1,5-dipolar cyclization of L(5). The spectral changes that originate from an intramolecular charge transfer (ICT) in the form of a pi(py)-->pi*(napy) transition can be tuned through acid/base-controlled switching for L(1)-L(3). A photoinduced isomerization for L(1)-L(3), 1, and 2 having flexible structures was observed under 365 nm light irradiation. Quantum chemical calculations revealed that the dinuclear complexes with structural asymmetry exhibit different metal-to-ligand charge-transfer transitions.
authors.affiliation: Key Laboratory of Photochemical Conversion and Optoelectronic Materials, HKU-CAS Joint Laboratory on New Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Peking 100190, China. fuwf@mail.ipc.ac.cn
authors.forename: Wen-Fu
authors.initials: WF
authors.lastname: Fu
authors.forename: Lin-Fang
authors.initials: LF
authors.lastname: Jia
authors.forename: Wei-Hua
authors.initials: WH
authors.lastname: Mu
authors.forename: Xin
authors.initials: X
authors.lastname: Gan
authors.forename: Jia-Bing
authors.initials: JB
authors.lastname: Zhang
authors.forename: Ping-Hua
authors.initials: PH
authors.lastname: Liu
authors.forename: Qian-Yong
authors.initials: QY
authors.lastname: Cao
authors.forename: Gui-Ju
authors.initials: GJ
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Quan
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Lv
authors.forename: Quan-Qing
authors.initials: QQ
authors.lastname: Xu
mesh_terms: D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D009287:Naphthyridines / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D055668:Photochemical Processes; D011789:Quantum Theory; D013057:Spectrum Analysis; D014753:Vinyl Compounds / Q000737:chemistry*
chemical_list: D009287:Naphthyridines; D009942:Organometallic Compounds; D014753:Vinyl Compounds; C551224:vinyl-1,8-naphthyridine; D003300:Copper