The propertles of the lowest electronic states of Michler’s hydrol blue, the prototypic dlarylmethane dye, were investigated byphotophysical measurements and CS-INDO CI calculations. MHB solutions showed very weak fluorescence emissions (&x 2.0-3.0~ 10m4) at room temperature and, from the sensitized T,-T. absorption spectrum of MHB in acetic acid, the T, formatlonquantum yield (&) was estimated to be below 3.5 x 1 O-‘. Starting from these observations, which point to a cyanme-like natureof MHB, a detailed theoretical study was carried out taking BMNC (bisdlmethylammononamethine cyanine) as the suitablereference chromophore. Calculations included the ground state conformation, the electronic So-S,, and T,-T, absorption spectraand the potential energy curves for twisting about one central C-C bond in the SO. T, and S, states. On the whole, the reportedresults support the existence of a close relationship between MHB and BMNC and indicate that the fast deactivation of the lowestexcited singlet state occurs via internal conversion from twisted configurations characterized by charge localization
|Anno di pubblicazione:||1992|
|Titolo:||Theoretical and experimental study of the electronic spectrumand photophysics of Michler’s hydrol blue|
|Autori:||I. Baraldi; A. Carnevali; F. Momicchioli; G. Ponterini|
|Appare nelle tipologie:||Articolo su rivista|
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