Delivery modulation in silica mesoporous supports via functionalization in the pore outlets with a Zn(II)–bis(2-pyridylmethyl)amine complex

This paper focuses on the study of the release behaviour of an entrapped dye (i.e. [Ru(bipy)(3)](2+)) in the presence of different anions from silica mesoporous supports functionalized in the external surface with Zn(II)-bis(2-pyridylmethyl)amine complexes (solid SZn). The Zn(II)-dipicolylamine complexes, anchored in the external surface of SZn, are too small to induce pore blockage and the loaded [Ru(bipy)(3)](2+) dye is freely to diffuse from the inner of the pores to the bulk solution. Addition of selected anions (F, Cl, Br, I, AcO, BzO, SO42, NO3, PO43, P2O72, ATP, ADP and AMP) modulates the release of the entrapped cargo. It was observed that the interaction of the Zn(II) complex with bulky organic phosphates (such as ATP, ADP and AMP), pyrophosphate and phosphate resulted in a remarkable inhibition of the [Ru(bipy)(3)](2+) dye. Small or poorly coordinating anions induced moderate or negligible inhibitions of [Ru(bipy)(3)](2+) release. The delivery observed was clearly related with the ability of the anion to form complexes with the Zn(II)-dipicolylamine groups and with the size and charge of the anion. (C) 2014 Elsevier B.V. All rights reserved.