title: Binding properties of solvatochromic indicators [Cu(X)(acac)(tmen)] (X = PF6- and BF4-, acac- = Acetylacetonate, tmen = N,N,N',N'-tetramethylethylenediamine) in solution and the solid state.
abstract: The solvatochromic indicator [Cu(acac)(tmen)(H 2O)].PF 6 ( 1.H 2O) has been synthesized and crystallographically characterized. 1.H 2O binds an H 2O molecule at the Cu(II) axial site, while the PF 6 (-) anion is coordination free. The binding properties of [Cu(PF 6)(acac)(tmen)] ( 1) and [Cu(BF 4)(acac)(tmen)] ( 2) have been investigated in solution and the solid state. The donor number of the PF 6 (-) anion (DN PF6) was determined from the UV-vis spectra of 1 in 1,2-dichloroethane. The value of DN PF6 of the PF 6 (-) anion is slightly larger than that of the tetraphenylborate anion (BPh 4 (-)), which is known as a noncoordinating anion. In the solid state, 1 and 2 reversibly bind and release H 2O molecules at the Cu(II) axial sites. The coordinated H 2O molecules in 2 are more easily removed than those in 1 because of the strong Lewis basicity of the BF 4 (-) anion compared to the PF 6 (-) ion. The lower melting point of 1 versus 2 is attributed to the loose binding of the PF 6 (-) anions to the Cu(II) centers, which induces the dynamic nature of the crystal.
authors.affiliation: Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan. noro@es.hokudai.ac.jp
authors.forename: Shin-Ichiro
authors.initials: S
authors.lastname: Noro
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Yanai
authors.forename: Susumu
authors.initials: S
authors.lastname: Kitagawa
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Akutagawa
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Nakamura