An NMR study and crystal structure of [{cis-Pt(NH3)2(9EtG-κN7)}2(µ-pz)][NO3]3 (9EtG = 9-ethylguanine) as a model compound for the 1,2-intrastrand GG crosslink†

Abstract

The platinum(II) complex [{cis-Pt(NH₃)₂(9EtG-κN⁷)}₂(µ-pz)][NO₃]₃·4H₂O 2 (pz = pyrazolate, 9EtG = 9-ethylguanine) was prepared from [{cis-Pt(NH₃)₂}₂(µ-OH)(µ-pz)][NO₃]₂ 1 and 9EtG. It was characterized by ¹H and ¹⁹⁵Pt NMR, and a crystal structure determination was performed. All ¹H NMR chemical shifts from the 9EtG ligands are observed at higher fields compared with those of free 9EtG, which is ascribed to their stacking interaction. The two 9EtG ligands are in a head-to-head orientation, and two intramolecular hydrogen bonds are observed between the ammine ligands and O⁶ oxygen atoms of the 9EtG ligands. The dihedral angle between the guanine planes is 10.8°, and the average distance is 3.89 Å.