title: Electronic and spectroscopic properties of avobenzone derivatives attached to ditungsten quadruple bonds.
abstract: From the reactions between W2(T(i)PB)4, where T(i)PB is 2,4,6-triisopropylbenzoate, and 2 equiv of acid, 4-formylbenzoic acid, HBzald, 4-(3-oxo-3-phenylpropanoyl)benzoic acid, HAvo, or 4-(2,2-difluoro-6-phenyl-2H-1λ(3),3,2λ(4)-dioxaborinin-4-yl)benzoic acid, HAvoBF2, three new compounds W2(T(i)PB)2(Bzald)2, I, W2(T(i)PB)2(Avo)2, II, and W2(T(i)PB)2(AvoBF2)2, III, have been prepared. As solid compounds I and II are blue while compound III is green. Characterization of these compounds has been carried out by means of (1)H NMR, MALDI-TOF MS, steady-state absorption and emission spectroscopies, and femtosecond and nanosecond transient absorption and time-resolved infrared spectroscopies. Compounds I and II have strong metal to ligand charge transfer, MLCT, transitions in the visible region of their spectra while compound III exhibits MLCT absorption in the near-infrared (λmax = 1017 nm). All three have S1 states that have corresponding lifetimes of ∼3-30 ps and are (1)MLCT in character. The triplet states are (3)MLCT with lifetimes in the range 3-10 ns. Density functional theory and time-dependent density functional theory were employed to perform electronic structure calculations in order to aid in the interpretation of these data. The spectroscopic properties of I and II are similar while the planarity of the ligand in III greatly lowers the energy of the MLCT state. The W2 unit enables direct observation of intersystem crossing from the (1)MLCT state to (3)MLCT state via the use of ultrafast spectroscopy.
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States.
authors.forename: Malcolm H
authors.initials: MH
authors.lastname: Chisholm
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States.
authors.forename: Terry L
authors.initials: TL
authors.lastname: Gustafson
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States.
authors.forename: William T
authors.initials: WT
authors.lastname: Kender
authors.affiliation: Department of Macromolecular Science and Engineering, Case Western Reserve University , 2080 Adelbert Road, Cleveland, Ohio 44106, United States.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Spilker
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Young
mesh_terms: D004583:Electrons; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D066244:Proton Magnetic Resonance Spectroscopy; D011789:Quantum Theory; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D014414:Tungsten / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D014414:Tungsten