The role of weak intermolecular interactions in photophysical behavior of isocoumarins on the example of their interaction with cyclic trinuclear silver(I) pyrazolate

Abstract

The complexation of 6-substituted isocoumarins with cyclic trinuclear silver pyrazolate was studied in solution and solid state. Spectral analysis of isocoumarins in concentrated solutions revealed the formation of dimers featuring π-π stacking supported by CH⋯O or CH⋯Cl hydrogen bonds. This behaviour has been proven by DFT calculations at ωB97XD level. The center of coordination of isocoumarine to silver-containing macrocycle is the carbonyl group. Experimental data demonstrate that CO groups interact with the silver macrocycle in the 1:1 ratio. The coordination of the carbonyl group to metallacycle observed in the solid state via cooperative CO⋯Ag3 interactions is typical for ketones. Different self-association abilities of isocoumarins lead to different coordination polymers of their complexes with the macrocycle: infinite stacks of {ABBA}∞ and {AB}∞ pattern were be obtained. The differences in supramolecular packing affect the emission properties of isocoumarins. Furthermore, the coordination of the carbonyl group to silver atoms leads to phosphorescence.