Adenosine monophosphate recognition by zinc-salophen complexes: IRMPD spectroscopy and quantum modeling study

Zn-salophen complexes are a promising class of fluorescent chemosensors for nucleotides and nucleic acids. We have investigated, by means of IRMPD spectroscopy experiments and quantum chemical calculations, the structure of the host-guest complexes formed by two efficient Zn-salophen receptors and dihydrogen phosphate or adenosine 5'-monophosphate (AMP) anions. In the host-guest complexes the phosphate group is bound with a Zn. O(phosphate) bond. In addition, a hydrogen bond can be formed between the PO. H group and one of the oxygen atoms of the salophen structure. The complexes with AMP anions are endowed with a hydrogen bonded coordination motif together with a weaker ??? interaction. It is thus confirmed that the marked changes of the spectroscopic emission properties of Zn-salophen when complexed with AMP can be associated with the existence of ??? stacking interactions between the salophen aromatic rings and those of the adenosine nucleobase.