“…25b It should be pointed out that, for all complexes studied herein, the shortest intercentroid distance corresponds to the interaction between the coumarin-lactone ring and the donor-benzenoid ring, furthermore, the mean interplanar distance between these two rings seems to define the magnitude of the CT interaction (3.50(3) Å and 399 nm, 3.5(2) Å and 406 nm, and 3.38(8) Å and 423 nm for the mean interplanar D-A distance and CTλ max of complexes 3, 4 and 5, respectively), in agreement with the results found in non heterocyclic D-A complexes. 15 The structural similarities between the H-bonded ABT-dimer and natural DNA base pairs, could help to explain the teratogen 26 and cytotoxic 27 activities as well as gene mutation protection activity 28 of several coumarin derivatives.…”