화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.112, No.6, 1150-1156, 2008
Separation of different hydrogen-bonded clusters by femtosecond UV-ionization-detected infrared spectroscopy: 1H-pyrrolo[3,2-h]quipoline center dot(H2O)(n=1,2) complexes
Experimental and theoretical studies are presented for complexes of water with 1H-pyrrolo[3,2-h]quinoline (PQ), a bifunctional compound acting simultaneously as a hydrogen-bond donor and acceptor. A 1: 1 complex, which is not fluorescent and only very short-lived in the electronically excited state, was analyzed by isolating the complex under supersonic jet conditions and characterizing its structure by infrared-induced ion depletion spectroscopy utilizing multiphoton ionization by femtosecond UV pulses (IR/fsMPI spectroscopy). On the other hand, a long-lived 1:2 complex was identified as the smallest microhydrate of PQ contributing to the laser-induced fluorescence excitation spectrum. Its structure was assigned by fluorescence-detected IR spectra and analyzed using density functional theory. The structures of the 1: 1 and 1:2 clusters are assigned to species in which the water molecule(s) form a hydrogen-bonded solvent bridge between the two functional groups. In accord. with calculations, both 1:1 and 1:2 PQ/water complexes reveal weaker hydrogen bonding than the analogous clusters of PQ with methanol.