title: Solvatochromic and ionochromic effects of Iron(II)bis(1,10-phenanthroline)dicyano: a theoretical study.
abstract: Solvatochromic and ionochromic effects of the iron(II)bis(1,10-phenanthroline)dicyano (Fe(phen)(2)(CN)(2)) complex were investigated by means of combined DFT/TDDFT calculations using the PBE and B3LYP functionals. Extended solvation models of Fe(phen)(2)(CN)(2) in acetonitrile and aqueous solution, as well as including interaction with Mg(2+), were constructed. The calculated vertical excitation energies reproduce well the observed solvatochromism in acetonitrile and aqueous solutions, the ionochromism in acetonitrile in the presence of Mg(2+), and the absence of ionochromic effect in aqueous solution. The vertical excitation energies and the nature of the transitions were reliably predicted after inclusion of geometry relaxation upon aqueous micro- and global solvation and solvent polarization effect in the TDDFT calculations. The two intense UV-vis absorption bands occurring for all systems studied are interpreted as transitions from a hybrid Fe(II)(d)/cyano N(p) orbital to a phenanthroline pi* orbital rather than a pure metal-to-ligand-charge transfer (MLCT). The solvatochromic and ionochromic blue band shifts of Fe(phen)(2)(CN)(2) were explained with preferential stabilization of the highest occupied Fe(II)(d)/cyano N(p) orbitals as a result of specific interactions with water solvent molecules or Mg(2+) ions in solution. Such interactions occur through the CN(-) groups in the complex, and they have a decisive role for the observed blue shifts of UV-vis absorption bands.
authors.affiliation: Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria. ivelina@svr.igic.bas.bg
authors.forename: Ivelina
authors.initials: I
authors.lastname: Georgieva
authors.forename: Adélia J A
authors.initials: AJ
authors.lastname: Aquino
authors.forename: Natasha
authors.initials: N
authors.lastname: Trendafilova
authors.forename: Paulo S
authors.initials: PS
authors.lastname: Santos
authors.forename: Hans
authors.initials: H
authors.lastname: Lischka