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Spectroscopy and Photophysics of Monoazaphenanthrenes I. Absorption and Fluorescence Spectra of Phenanthridine and 7,8-Benzoquinoline

100%

Norek M., Dresner J., Prochorow J.

Acta Physica Polonica A

2003

vol. 104

issue 5

425-439

The absorption and fluorescence spectra of phenaentridine and 7,8-benzoquinoline have been measured in liquid solutions of non-polar, aprotic hydrocarbon solvents (n-hexane and cyclohexane) and in strongly polar (and hydrogen-bonding) methanol. The analysis of the Stokes' shift between absorption and fluorescence spectra has shown that for both molecules the observed solvent effects on their absorption and fluorescence spectra can be described in terms of universal solvent-solute interactions (no evidence of specific solvent-solute interactions, of the type of hydrogen bond formation with participation of lone-pair electrons of nitrogen atom, has been found). On the other hand, the measured decay time profiles of fluorescence are visibly longer in methanol solution than in non-polar, aprotic solvents and these observations are consistent with the observed increase in fluorescence intensity of both molecules in strongly polar methanol solution. The radiative lifetimes of the first excited singlet state do not differ noticeably for both molecules, but it has turned out that in the case of phenanthridine the nonradiative processes are getting less effective in methanol solution than in the case of 7,8-benzoquinoline, which can presumably be related to the role of different position of the substitution of nitrogen atom in these two molecules.

Purely Electronic and Vibronic Fluorescence Excitation of Single Terrylene Molecules in a Naphthalene Crystal

88%

Banasiewicz M., Dresner J., Morawski O., Wiącek D., Kozankiewicz B.

Acta Physica Polonica A

2007

vol. 112

issue S

S-85-S-94

Fluorescence excitation spectra of spatially resolved single terrylene molecules in a naphthalene crystal were studied at 5 K as a function of exciting laser light intensity. The fully saturated fluorescence detection rate for purely electronic transition (0,0) was found to be about twice smaller than that for the two main vibronic components located 239 and 251 cm^{-1} above. This relation is fulfilled when the triplet population rate k_{23} is much weaker than the depopulation rate k_{31}. We propose that the weak fluorescence excitation lines observed at the frequencies of 38, 67, 97, and 145 cm^{-1} correspond to nontotally symmetric low-frequency vibration modes of terrylene.

Photoinduced Charge-Transfer Reactions of Tricyanoethlene with Aromatic Hydrocarbon Electron Donors. I. Emission Studies of Naphthalene-Tricyanoethylene Exciplex

76%

Dresner J., Kwapisz K., Deperasińska I., Prochorow J., Bruni P., Giardina A., Tosi G.

Acta Physica Polonica A

2002

vol. 102

issue 3

443-468

The fluorescence quenching of a series of aromatic hydrocarbon electron donors by an electron acceptor tricyanoethylene has been observed. The quenching mechanism is consistent with the charge-transfer (or electron-transfer) mechanism, as indicated by the appearance of a new, broad, and structureless exciplex emission band. Detailed, steady-state, and time-resolved emission studies of the kinetics and thermodynamics of exciplex formation and relaxation have been performed for naphthalene-tricyanoethylene system. It was found that the kinetics of monomer-exciplex equilibrium for this system, in a non-polar solvent (n-hexane), can be described in terms of a simple two-state photokinetic scheme. Within such a scheme, under conditions of the present experiment, napthalene-tricyanoethylene system approaches the limits under which exciplex formation is very effective - it becomes exclusively diffusion-controlled and at the same time a competitive process of thermal dissociation of exciplex ceases to operate. This leads to a very rarely observed reversal of physical meaning of the decay parameters which are describing the rise and the decay of exciplex fluorescence.

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3 Acta Physica Polonica A

1 2007

1 2003

1 2002

3 Dresner J.

2 Prochorow J.

1 Banasiewicz M.

1 Bruni P.

1 Deperasińska I.

1 Giardina A.

1 Kozankiewicz B.

1 Kwapisz K.

1 Morawski O.

1 Norek M.

1 Tosi G.

1 Wiącek D.

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Spectroscopy and Photophysics of Monoazaphenanthrenes I. Absorption and Fluorescence Spectra of Phenanthridine and 7,8-Benzoquinoline

Purely Electronic and Vibronic Fluorescence Excitation of Single Terrylene Molecules in a Naphthalene Crystal

Photoinduced Charge-Transfer Reactions of Tricyanoethlene with Aromatic Hydrocarbon Electron Donors. I. Emission Studies of Naphthalene-Tricyanoethylene Exciplex