Mesoporous Silica Functionalized by Cyclam–Metal Groups: Spectroscopic Studies and Numerical Modeling

Abstract

Mesoporous silica functionalized by cyclam–metal molecules were investigated by spectroscopic methods including Raman, IR, UV–VIS absorption and EPR technique. To analyse quantitatively the physical features, numerical models were developed using the density functional theory method. Thus, the construction of molecular geometries and their optimisation analysis were achieved on the cyclam–metal molecules in vacuum as well as constrained by the host mesoporous silica matrixes. In this context and with regard to the paramagnetic nature of the metals chelated by cyclam molecules, EPR technique allows probing the metal environments which can be compared to theoretical results inferred from numerical models. The vibrational and optical properties were exhaustively investigated and the assignment of the main features was quantitatively discussed thanks to the carried out numerical analyses. The developed approach point out the possibility to define a targeted application of such functional materials based on the possibility to fine tune the absorption features in a wide wavelength range by stabilizing defined configurations of the cyclam–metal groups.