Self‐Association of [Pt II (1,10‐Phenanthroline)( N ‐pyrrolidyl‐ N ‐(2,2‐dimethylpropanoyl)thiourea)] + and Non‐Covalent Outer‐Sphere Complex Formation with Fluoranthene through π–Cation Interactions: A High‐Resolution 1 H and DOSY NMR Study

Competing outer‐sphere self‐association of [Pt II (1,10‐phenanthroline)( N ‐pyrrolidyl‐ N ‐(2,2‐dimethylpropanoyl)thiourea)] + Cl – (M) and the hetero‐association of M with fluoranthene (F) have been investigated by means of the significant concentration dependence of 1 H NMR chemical shifts as well as by diffusion coefficients obtained from DOSY NMR spectroscopy. The NMR spectroscopic data is only consistent with the formation of a “dimer” M ··· M aggregate according to 2M [rlhar2] M 2 in acetonitrile at several temperatures, with a calculated K D of ca. 46 ± 7 M –1 at 273.5 K. In the presence of the aromatic molecule fluoranthene, relatively strong, presumably π–cation‐type interactions between M and F according to M + F [rlhar2] MF ( K B  ≈ 67 ± 7 M –1 at 273.5 K) occur in acetonitrile. The calculated Δ r H ° and Δ r S ° for M ··· M (–25129 ± 3112 and –61 ± 11 J mol –1 ) and M ··· F (–13560 ± 3180 and –17 ± 11 J mol –1 , respectively) is indicative of π–cation interactions. Interestingly any potential F ··· F aggregation interactions are negligible for the fluoranthene concentration range up to 0.1 M , indicating that non‐covalent π–π interactions between fluoranthene molecules 2F [rlhar2] F 2 are, in contrast to π–cation interactions, negligible under these conditions in solution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)