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

Abstract

Mesoporous silica functionalized by cyclammetal 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.

Chiral Discrete and Polymeric Uranyl Ion Complexes with (1R,3S)-(+)-Camphorate Ligands: Counterion-Dependent Formation of a Hexanuclear Cage

“…While this argument is based on solution spectroscopic data, it is known that the solid state spectra of the Ni II and Cu II complexes of unfunctionalised cyclam closely match those in solution. 66 The PLQY for complex 4 is similar to that of 24% we have measured under the same conditions for uranyl nitrate hexahydrate, and is one of the largest measured up to now in the family of uranyl carboxylate complexes, to be compared for example with 13% for 67 and 58% for [UO2(HL)(H2O)] (H3L = benzene-1,3,5-tricarboxylic acid). 68 We have discussed elsewhere 41 the possibility that energy transfer between close uranyl centres might prolong excited state lifetimes and thus that U⋅⋅⋅U separations within lattices may be important criteria in relation to PLQY values but the shortest U⋅⋅⋅U distance does not seem to be a relevant parameter in the case of complex 4 since, at 8.0460(3) Å (interchain), it is indeed larger than the values measured in the two most strongly emitting complexes cited above (5.511 and 5.232 Å, respectively), but comparable to distances in some much more weakly emitting species.…”

Use of Modified Colloids and Membranes to Remove Metal Ions from Contaminated Solutions

“…The BET surface area was S BET = 627 m 2 g −1 , the total pore volume was V p = 0.52 cm 3 g −1 , the mean pore diameter was D p = 36 Å, and the mean thickness of the pore walls was 70 Å. The structure of SiO 2 -cyclam is very porous and consists of parallel and well-aligned pores as previously shown by TEM [44]. The infrared and Raman spectra of SiO 2 -cyclam composites can also be found elsewhere [44].…”

“…The structure of SiO 2 -cyclam is very porous and consists of parallel and well-aligned pores as previously shown by TEM [44]. The infrared and Raman spectra of SiO 2 -cyclam composites can also be found elsewhere [44].…”

“…Thus, the specific surface area of the silica particles decreased considerably after modification since it decreased from 200 m 2 g −1 to 5 m 2 g −1 [43]. The degree of ionization of the carboxyl groups of these composites was determined and found to be 0.74 using titration experiments and the isoelectric point of SiO2-CMCS composite was found to be 6.0 using zeta-potential measurements [44]. The morphology of SiO2-cyclam composites was also studied and it was found by SEM that these composites consist in small grains of the silica particles distributed heterogeneously in the CMCS matrix.…”

“…The morphology of SiO2-cyclam composites was also studied and it was found by SEM that these composites consist in small grains of the silica particles distributed heterogeneously in the CMCS matrix. The infrared and 1 H RMN spectra of SiO2-CMCS composites can also be found elsewhere [19,44].…”