Steric hindrance in the gas phase singlet electronic energy transfer: From naphthalene to thetranshyphen;azobutane isomers

摘要

The singlet intermolecular energy transfer rates from naphthalene (S1, sim;91 kcal/mol) to the varioustranshyphen;azobutane isomers have been measured in the gas phase. The first excited singlet states of these azobutane isomers lie below sim;70 kcal/mol. The rate constants for singlet collisional energy transfer (kc) are 30.3plusmn;2.6, 18.9plusmn;0.9, 12.6plusmn;1.0, and 3.2plusmn;0.3 in units of 1010Mminus;1sdot;secminus;1, for the accepter series azohyphen;nhyphen;butane, azoisobutane, azohyphen;sechyphen;butane, and azohyphen;terthyphen;butane, respectively. The tenfold decrease in the rates of energy transfer through this series have been attributed to increasing steric inhibition of the electron exchange contribution to singletndash;singlet electronic energy transfer.