Selective binding of benzenediol derivatives by simultaneous non-covalent interactions in bis-Pt(II) aza-aromatic host-guest system

摘要

We have designed and synthesized a new ligand, 6-(2-pyridinyl)-4-[3′- (3-pyridinyl)[1,1′-biphenyl]-3-yl]-2,2′-bipyridine (2). 2 reacted with Pt(cod)(MeCN)_2(BF_4)_2 to quantitatively give the molecular dimer, 1·BF_4 (2_2·Pt~ (II)_2·4BF_4~-), by self-assembly. The ~1H NMR and UV-vis titration showed that the complexation affinity of 1·BF_4 toward benzenediol guests decreases in the order para > meta > ortho. The structural analysis revealed that the π-π stacking interactions and multiple CH?O hydrogen bonds make the benzenediol binding favorable. DFT calculations showed that complexation with Pt(II) leads to a unique charge distribution in 1 creating more positive sites inside the cavity that provides a strong binding site for benzenediols. The macrocyclic preorganization effect, induced-fit complexation mechanism, Coulombic interactions, such as π-π stacking interactions, and CH?O hydrogen bonding contribute to the benzenediol recognition.