NHC Tetranuclear Silver(I) Complexes and Intramolecular Extended π–π Interactions

A series
of new acyclic tetrazolium salts featuring a central anthracence
building block which were 9,10-substituted with (N-R-azoliumCH2CH2)2NCH2– groups
were prepared (azolium = benzimidazolium or imidazolium, R = picolyl,
ethyl, nbutyl, or benzyl). These tetrazolium
salts were metalated with silver­(I) leading to four novel NHC tetranuclear
complexes 1–4. Molecular structures
of 1–4 and one tetraimidazolium salt L1H4·(HgI4)2 were established by 1H NMR, 13C NMR spectroscopy and X-ray crystallography. Silver­(I) η3-arene interactions exist in complex 1. Each
molecule of complexes 2–4 contains
one 42-membered and two 21-membered macrometallocycles. It was interesting
to observe intramolecular extended π–π interactions
originated from imidazole–anthracene–anthracene–imidazole
in complexes 3 and 4. In addition, the fluorescence
emission spectra of the complexes and the tetrazolium salts were studied.