title: An ab initio study of substituent effects on the excited states of purine derivatives.
abstract: Several excited singlet electronic states of purine nucleobases and related derivatives have been calculated using high-level multireference perturbation theory methods. Purine derivatives with one or two amino or carbonyl groups substituted at positions C(2) and/or C(6) of the purine ring have been included in the study. The effect of the substituents on excited-state energies and wave functions is examined. Some trends have been observed, such as the fact that substitution at the C(2) position decreases the energy of the first pi --> pi* state considerably. Although basic qualitative features of the effects can be explained with the simple frontier molecular orbital theory, ab initio calculations are required to describe the effects quantitatively.
authors.affiliation: Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Mburu
authors.forename: Spiridoula
authors.initials: S
authors.lastname: Matsika
mesh_terms: D015075:2-Aminopurine / Q000031:analogs & derivatives / Q000737:chemistry; D000225:Adenine / Q000737:chemistry; D004583:Electrons; D005740:Gases / Q000737:chemistry; D006147:Guanine / Q000737:chemistry; D019271:Hypoxanthine / Q000737:chemistry; D007536:Isomerism; D011687:Purines / Q000737:chemistry*; D011789:Quantum Theory; D019820:Xanthine / Q000737:chemistry
chemical_list: D005740:Gases; D011687:Purines; D019820:Xanthine; D019271:Hypoxanthine; D015075:2-Aminopurine; C007300:2,6-diaminopurine; D006147:Guanine; C008183:isoguanine; D000225:Adenine; C030985:purine