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>Investigation of singlethyphen;triplet transitions by phosphorescence excitation spectroscopy. X A simple agr;, bgr;hyphen;unsaturated ketone
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Investigation of singlethyphen;triplet transitions by phosphorescence excitation spectroscopy. X A simple agr;, bgr;hyphen;unsaturated ketone
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机译：Investigation of singlethyphen;triplet transitions by phosphorescence excitation spectroscopy. X A simple agr;, bgr;hyphen;unsaturated ketone
Xhyphen;ray diffraction techniques and Patterson methods have been used to determine the crystal structure of the simple conjugated enone, ketoneI. The crystals studied belong to space groupP1withaequals; 9.365(6),bequals; 6.578(4),cequals; 8.321(5), agr; equals; 101.70(3), bgr; equals; 101.55(3), and ggr; equals; 101.37(3). Least squares refinement of 836 counterhyphen;collected, unique reflections havingverbar;thinsp;Fthinsp;verbar;22.5sgr;lpar;verbar;thinsp;Fthinsp;verbar;2rpar;led to a final value of the conventionalR1factor (based onF) of 5.8percnt;. The structure consists of rather loosely packed, strain free bicyclic molecules, in which the enone chromophore is planar. Phosphorescence excitation spectroscopy was used to obtain the polarized singlethyphen;singlet and singlethyphen;triplet absorption spectra of oriented crystals. The important results are: (i) The ordering of excited states in this molecule is1lpar;n, pgr;*rpar;3lpar;n, pgr;*rpar;3lpar;pgr;,thinsp;pgr;*rpar;. (ii) Polarization measurements and Franckhyphen;Condon considerations indicate that the difference in geometry between the3(pgr;, pgr;*) state and the gound state is small. (iii) The1(n, pgr;*) state appears to be the exclusive source of intensity for the origin band of theTpgr;,pgr;*larr; S0transition. (iv) TheTpgr;,pgr;*larr; S0absorption spectrum indicates that there is extensive vibronic mixing between the3(pgr;, pgr;*) state and the nearly degenerate3(n, pgr;*) state. (v) Vibronic mixing is much less important in the emission spectrum. Consequently, theTpgr;,pgr;*rlarr2; S0absorption and emission spectra are far from mirrorhyphen;image symmetric, and the observed radiative lifetime of the triplet state is quite different from that computed from theTlarr; S0absorption. (vi) The polarization of theTn,pgr;*larr; S0transition can be accounted for in terms of spinhyphen;orbit coupling between the3(n, pgr;*) and1(pgr;, pgr;*) states. (vii) The complete absence of vibrational structure in theTn,pgr;*larr; S0spectrum is attributed to extensive mixing between the3(n, pgr;*) state and degenerate vibronic levels of the lower lying3(pgr;, pgr;*) state. (viii) The significant inhyphen;plane polarization in theSn,pgr;*larr; S0transition is attributed to perturbations of the planar enone chromophore by out of plane hydrogen and methyl groups which introduce intensity that is inhyphen;plane polarized but perpendicular to the Cdblbnd;O axis. (ix) Much of the intensity in theSn,pgr;*larr; S0transition is vibronically induced and polarized along the Cdblbnd;O axis.
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