Near-Infrared Laser-Induced Generation of Three Rare Conformers of Glycolic Acid

Halasa A., Lapinski L., Reva I., Rostkowska H., Fausto R., Nowak M. J.

JOURNAL OF PHYSICAL CHEMISTRY A, cilt.118, sa.30, ss.5626-5635, 2014 (SCI-Expanded, Scopus)

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 118 Sayı: 30
  • Basım Tarihi: 2014
  • Doi Numarası: 10.1021/jp5051589
  • Dergi Adı: JOURNAL OF PHYSICAL CHEMISTRY A
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.5626-5635
  • İstanbul Kültür Üniversitesi Adresli: Hayır

Özet

Structural transformations were induced in conformers of glycolic acid by selective excitation with monochromatic tunable near-infrared laser light. For the compound isolated in Ar matrixes, near-IR excitation led to generation of two higher-energy conformers (GAC; AAT) differing from the most stable SSC form by 180 rotation around the C C bond. A detailed investigation of this transformation revealed that one conformer (GAC) is produced directly from the near-IR-excited most stable conformer. The other higher-energy conformer (AAT) was effectively generated only upon excitation of the primary photoproduct (GAC) with another near-IR photon. Once these higher-energy conformers of glycolic acid were generated in an Ar matrix, they could be subsequently transformed into one another upon selective near-IR excitations. Interestingly, no repopulation of the initial most stable SSC conformer occurred upon near-IR excitation of the higher-energy forms of the compound isolated in solid Ar. A dramatically different picture of near-IR-induced conformational transformations was observed for glycolic acid isolated in N-2 matrixes. In this case, upon near-IR excitation, the most stable SSC form converted solely into a new conformer (SST), where the acid OH group is rotated by 180 degrees. This conformational transformation was found to be photoreversible. Moreover, SST conformer, photoproduced in the N-2 matrix, spontaneously converted to the most stable SSC form of glycolic acid, when the matrix was kept at cryogenic temperature and in the dark.