Symmetry breaking in the relaxed S1 excited state of bianthryl derivatives in weakly polar solvents

被引:122
作者
Piet, JJ [1 ]
Schuddeboom, W [1 ]
Wegewijs, BR [1 ]
Grozema, FC [1 ]
Warman, JM [1 ]
机构
[1] Delft Univ Technol, IRI, Radiat Chem Dept, NL-2629 JB Delft, Netherlands
关键词
D O I
10.1021/ja004341o
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The flash-photolysis time-resolved microwave conductivity technique (FP-TRMC) has been used to investigate the nature of the relaxed S-1 state of 9,9'-bianthryl (AA), 10-cyano-9,9'-bianthryl (CAA), and 10,10'-dicyano-9,9'-bianthryl (CAAC). Changes in both the-real, Delta epsilon' (dielectric constant), and imaginary, Delta epsilon " (dielectric loss), components of the complex permittivity have been measured. The dielectric loss transients conclusively demonstrate the dipolar nature of S1 for all three compounds in the pseudopolar solvents benzene and 1,4-dioxane, and-even in the nonpolar solvents n-hexane and cyclohexane. The required symmetry breaking is considered to result from density and structural fluctuations,in the Solvent environment. The dipole relaxation times for AA (CAAC) are ca. 2 ps for the:alkanes and 7.9 (5.3) and 14 (14) ps for benzene and dioxane, respectively. The time scale of dipole relaxation for the symmetrical compounds is much shorter than that for rotational diffusion and is attributed to intramolecular, flip-flop dipole reversal via a neutral excitonic state. The dipole moment of the transient dipolar state is estimated to be ca. 8 D, that is much lower than the value of ca..20 D determined- from the:solvatochromic shifts in the fluorescence in intermediate to highly polar solvents which corresponds to close to complete charge separation. For the asymmetric compound, CAA, a dipole moment close to 20 D is found in all solvents, including n-hexane. Dipole relaxation in this case occurs on a time scale of several hundred:picoseconds and is controlled mainly by diffusional rotation of the molecules. The mechanism and kinetics of formation of the dipolar excited states are discussed in the light of these results.
引用
收藏
页码:5337 / 5347
页数:11
相关论文
共 39 条
[1]   A STUDY ON EXCITED-STATES DIPOLE-MOMENTS OF 9,9'-BIANTHRYL [J].
BAUMANN, W ;
SPOHR, E ;
BISCHOF, H ;
LIPTAY, W .
JOURNAL OF LUMINESCENCE, 1987, 37 (04) :227-233
[2]   Solvent dependence of the emission from species consisting of two identical moieties [J].
Beens, Henk ;
Weller, Albert .
CHEMICAL PHYSICS LETTERS, 1969, 3 (09) :666-668
[3]   PHOTON-INDUCED MOLECULAR CHARGE SEPARATION STUDIED BY NANOSECOND TIME-RESOLVED MICROWAVE CONDUCTIVITY [J].
DEHAAS, MP ;
WARMAN, JM .
CHEMICAL PHYSICS, 1982, 73 (1-2) :35-53
[4]   REFERENCE MATERIALS FOR FLUORESCENCE MEASUREMENT [J].
EATON, DF .
PURE AND APPLIED CHEMISTRY, 1988, 60 (07) :1107-1114
[5]   INFLUENCE OF CYANO SUBSTITUENTS ON THE EFFECTIVE S1 TORSIONAL POTENTIALS OF SYMMETRICAL AND SYMMETRY-DISTURBED DERIVATIVES OF 9,9'-BIANTHRYL IN CONDENSED MEDIA [J].
ELICH, K ;
LEBUS, S ;
WORTMANN, R ;
PETZKE, F ;
DETZER, N ;
LIPTAY, W .
JOURNAL OF PHYSICAL CHEMISTRY, 1993, 97 (39) :9947-9955
[6]   Excitonic and charge transfer states in oligomeric 9,10-anthrylene chains [J].
Fritz, R ;
Rettig, W ;
Nishiyama, K ;
Okada, T ;
Muller, U ;
Mullen, K .
JOURNAL OF PHYSICAL CHEMISTRY A, 1997, 101 (15) :2796-2802
[7]   MICROSCOPIC SOLVATION OF ACETONE TO 9,9'-BIANTHRYL STUDIED IN A FREE JET - POLAR EXCITED-STATE FORMATION [J].
HONMA, K ;
ARITA, K ;
YAMASAKI, K ;
KAJIMOTO, O .
JOURNAL OF CHEMICAL PHYSICS, 1991, 94 (05) :3496-3503
[8]   Ultrafast electron transfer in acceptor substituted bianthryl derivatives [J].
Jurczok, M ;
Plaza, P ;
Rettig, W ;
Martin, MM .
CHEMICAL PHYSICS, 2000, 256 (01) :137-148
[9]   ELECTRON-TRANSFER TIMES ARE NOT EQUAL TO LONGITUDINAL RELAXATION-TIMES IN POLAR APROTIC-SOLVENTS [J].
KAHLOW, MA ;
KANG, TJ ;
BARBARA, PF .
JOURNAL OF PHYSICAL CHEMISTRY, 1987, 91 (26) :6452-6455
[10]   SOLVENT EFFECT IN AN ISOLATED SOLVATED MOLECULE IN A FREE JET - INTRAMOLECULAR CHARGE-TRANSFER STATE OF SOLVATED 9,9'-BIANTHRYL [J].
KAJIMOTO, O ;
YAMASAKI, K ;
ARITA, K ;
HARA, K .
CHEMICAL PHYSICS LETTERS, 1986, 125 (02) :184-188