STRUCTURE OF 5-[2-(3-INDOLYL)ETHYL]-1,3-DIMETHYLURACIL 1,3-DIMETHYLURACIL CIS,SYN-CYCLOBUTANE PHOTODIMER

4a-[2-(3-Indolyl)ethyl]-1,3,6,8-tetramethyl-4a,4b,8a,8b-tetrahydrocyclobuta[1,2-d:4,3-d']dipyrimidine-2,4,5,7(1H,3H,6H,8H)-tetrone, C22H25N5O4, M(r) = 423.52, triclinic, P1BAR, a = 8.116 (4), b = 15.888 (6), c = 16.226 (7) angstrom, alpha = 87.05 (3), beta = 86.28 (3), gamma = 87.79 (3)-degrees, V = 2083.8 (15) angstrom 3, Z = 4, D(m) = 1.34, D(x) = 1.35 g cm-3, lambda-(Mo K-alpha) = 0.71073 angstrom, mu = 0.9 cm-1, F(000) = 896, T = 298 K, R = 0.0872 for 3779 observed data [F(o) > 3-sigma-(F(o))] of 7155 unique data collected. Hydrogen bonding is observed between the indolyl N-H and the uracil C(4)-O as well as attractive interaction between the uracil C(5)-H and C(4)-O atoms. It is assumed that van der Waals interactions hold layers of hydrogen-bonded molecules that lie parallel to the (011).