Assembly and Properties of Donor/Acceptor–Functionalized 2,6‐Bisethynylpyridines; Investigations of Through‐Bond and Through‐Space Charge Transfer Behavior

Introduction of Ag(I) cations to 2,6‐bisethynylpyridine units decorated with electron‐donating ( N , N ‐dimethylaniline) and electron‐accepting (1,3‐dinitrobenzene) groups yields electronic changes consistent with the formation of distinct metal‐organic complexes. Although the formation of these complexes is dynamic—allowing for the possibility of contributors with several different ligand:metal stoichiometries— 1 H NMR titration data point to significant contributions from a 2:1 ligand:metal complex. Mutual shielding of the donor and acceptor arms in the 2:1 complex leads to sharp decreases in 1 H NMR chemical shifts of hydrogens on these rings. Though the changes in electronic properties and evidence of mutual shielding infer formation of a complex with a close spatial relationship of donor and acceptor units, the electronic effects that would be expected for through‐space charge transfer are not clearly distinguishable from through‐bond electronic effects. Protonation of the central pyridines illuminates how through‐bond interactions of the N , N ‐dimethylaniline arms with a positively charged central pyridine tend to dominate the electronic profile of each ligand. X‐ray crystallographic studies of an Ag(I) complex of a donor‐acceptor system illustrate notable contacts between N , N ‐dimethylaniline and 1,3‐dinitrobenzene units.