The nature of the Ag-I center dot center dot center dot Ag-I interaction in different Ag(NH3)(2) dimers embedded in supramolecular

An isolated silver(I) ammonia monomer, a dimer, and a novel dimer containing an intercalated water molecule have been embedded as guests in supramolecular frameworks, [Ag(NH3)(2)][(H(2)thpe)(H(3)thpe)]center dot MeCN (1), [{Ag(NH3)(2)}(2)][(H(2)thpe)(2)]center dot 4.25H(2)O (2), and [{Ag(NH3)(2)}-H2O-{Ag(NH3)(2)}]- [(H(2)thpe)(2)]center dot benzene (3) (H3THPE= tris(hydroxyphenyl)ethane). The [{Ag(NH3)(2)}(2)](2+) dimer is not stable as an isolated entity, but is stabilized by hydrogen bonding in the supramolecular framework. The water-intercalated silver(I) ammonia dimer, which constitutes a novel species, is also subject by hydrogen bonding in concentrated solutions. The destabilization energy of the dimer relative to isolated monomers is calculated to be 300 kJ mol(-1) by both perturbation methods and DFT theory. For the water-intercalated dimer it is calculated to be approximate to 200 kJ mol(-1) according to the BSSE-corrected MP2 calculation. The different aggregate states show a dramatic variation of absorption and emission properties, in accordance with the concentration dependent red-shift observed in solutions. Natural-bond-orbital analysis shows that the disilver-ammonium-aquo sandwich cation in 3 is stabilized by interaction between the it lone pair orbital on the oxygen atom of the water molecule and Ag-1-N o antibonding molecular orbital.