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

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 (1)H 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 pi-pi 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 pi-pi stacking interactions, and CH...O hydrogen bonding contribute to the benzenediol recognition.