@article {1145,
	title = {Discrimination in the solid-state photodimerization of 1-methyl-5,6-diphenylpyrazin-2-one},
	journal = {European Journal of Organic Chemistry},
	number = {5},
	year = {2005},
	note = {ISI Document Delivery No.: 903LHTimes Cited: 5Cited Reference Count: 18},
	month = {Feb},
	pages = {847-853},
	type = {Article},
	abstract = {1-Methyl- and 1-ethyl-5,6-diphenylpyrazin-2-one crystallize in two modifications, one of which is light-stable and the other light-sensitive. The light-sensitive modification is known to undergo photodimerization in the solid state. This polymorph crystallizes in the monoclinic space group P2(1) with two crystallographically independent molecules in the asymmetric unit. The molecules are packed in stacks running parallel to the unique b axis. The two independent molecules are arranged alternately along the stack. In principle, there are two different pairs of molecules within a stack that can undergo photodimerization, and each should form a different enantiomer. A large crystal was irradiated and a solution of the product was separated by HPLC. The optical purity of the (+)-enantiomer sample was estimated to be greater than 90 \%. This finding indicates that only one of the two pairs undergoes photoreaction. The structure of a single crystal of the pyrazinone was elucidated by X-ray diffractometry before and after irradiation with a laser at a wavelength of 488 nm to 19 \% conversion. The results of the crystal-structure determinations provide additional evidence that only one of the two pairs of molecules undergoes photodimerization although there are no significant differences between the distances between the reacting centers. Furthermore, the latter results suggest that weak hydrogen bonds are a dominant factor that determines which of the two pairs is dimerized upon irradiation. ((C) Wiley-VCH Verlag GmbH \& Co. KGaA, 69451 Weinheim, Germany, 2005).},
	keywords = {chirality, crystal structure, DIMERIZATION, enantioselectivity, PHOTOCHEMISTRY, SINGLE-CRYSTAL PHOTODIMERIZATION, solid-state reactions},
	isbn = {1434-193X},
	url = {<Go to ISI>://000227426900009},
	author = {Kaftory, M. and Shteiman, V. and Lavy, T. and Scheffer, J. R. and Yang, M. and Enkelmann, V.}
}
@article {565,
	title = {1-Methyl-5,6-diphenylpyrazine-2(1H)-thione},
	journal = {Acta Crystallographica Section C-Crystal Structure Communications},
	volume = {58},
	year = {2002},
	note = {ISI Document Delivery No.: 536YDTimes Cited: 2Cited Reference Count: 11Part 4},
	month = {Apr},
	pages = {O220-O222},
	type = {Article},
	abstract = {The title compound, C17H14N2S, crystallizes in a triclinic unit cell, with two crystallographically independent molecules in the asymmetric unit. The two independent molecules pack in the same sense and form segregated layers along the c axis. The crystal is light-stable and no dimers are formed under irradiation. The intermolecular distances between the potential reactive centers (the C-3 and C-5 ring positions) are 4.093 (4) and 5.643 (4) Angstrom for molecule A, and 4.081 (4) and 5.614 (4) Angstrom for molecule B.},
	keywords = {DIMERIZATION, SOLID-STATE},
	isbn = {0108-2701},
	url = {<Go to ISI>://000174728700038},
	author = {Zolotoy, A. B. and Botoshansky, M. and Kaftory, M. and Scheffer, J. R. and Yang, J.}
}
@article {5046,
	title = {Aggregation studies of benzoporphyrin derivative},
	journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie},
	volume = {79},
	number = {5-6},
	year = {2001},
	note = {ISI Document Delivery No.: 456EVTimes Cited: 11Cited Reference Count: 33},
	month = {May},
	pages = {1068-1074},
	type = {Article},
	abstract = {The photophysical properties of a ring B benzoporphyrin derivative 1,3-diene dimethylester were investigated in solution (water-DMSO mixtures). At low proportions of water in DMSO, the diester obeys Beer{\textquoteright}s law at all pH values and ionic strengths investigated. For solvent systems containing more than 30\% water, the extent of deviation from Beer{\textquoteright}s law as a function of porphyrin concentration is attributed to formation of porphyrin dimers. Dimerization equilibrium constants (Kd) have been determined in different percentage of solvent mixtures, using absorption and fluorescence spectroscopies, and were found to exhibit a linear correlation between log (Kd) and the inverse of the dielectric constant (log (Kd) = 24.6 - 1060.4 x 1/epsilon (mix)). This equation permits the calculation of Kd in mixtures of water-DMSO.},
	keywords = {AGGREGATION, benzoporphyrin, BPD, DERIVATIVE, DIMERIZATION, FLUORESCENCE, PHOTODYNAMIC THERAPY, PHOTOSENSITIZERS, porphyrins, SPECTROSCOPY, therapy},
	isbn = {0008-4042},
	url = {<Go to ISI>://000170070900079},
	author = {Delmarre, D. and Hioka, N. and Boch, R. and Sternberg, E. and Dolphin, D.}
}
