title: Ferrocene-donor and 4,5-dicyanoimidazole-acceptor moieties in charge-transfer chromophores with π linkers tailored for second-order nonlinear optics.
abstract: A series of new nonlinear optical chromophores (1-15) that were comprised of ferrocene-donor and 4,5-dicyanoimidazole-acceptor moieties and various π linkers of different length were synthesized. Support for the presence of significant DA interactions in these NLO-phores was obtained from the evaluation of the quinoid character of the 1,4-phenylene moieties and their electronic absorption spectra, which featured intense high-energy (HE) bands that were accompanied by less-intense low-energy (LE) bands. The redox behavior of these compounds was investigated by cyclic voltammetry (CV) and by rotating-disc voltammetry (RDV); their electrochemical gaps decreased steadily from 2.64 to 2.09 V. In addition to the experimentally obtained data, DFT calculations of their absorption spectra, HOMO/LUMO levels, and second-order polarizabilities (β) (-2ω,ω,ω) were performed. A structure-property relationship study that was performed by systematically altering the π linker revealed that the intramolecular charge-transfer and nonlinear optical properties of these inorganic-organic hybrid D-π-A systems (1-15) were primarily affected by: 1) The presence of olefinic/acetylenic subunits; 2) the length of the π linker; and 3) the spatial arrangement (planarity) of the π linker.
authors.affiliation: Institute of Organic Chemistry and Technology, Faculty of Chemical Technology, University of Pardubice, Pardubice, Studentská 573, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Kulhánek
authors.forename: Filip
authors.initials: F
authors.lastname: Bureš
authors.forename: Wojciech
authors.initials: W
authors.lastname: Kuznik
authors.forename: Iwan V
authors.initials: IV
authors.lastname: Kityk
authors.forename: Tomáš
authors.initials: T
authors.lastname: Mikysek
authors.forename: Aleš
authors.initials: A
authors.lastname: Růžička