ChemInform Abstract: Synthesis and Characterization of Mn-Containing Cubic Mesoporous MCM-48 and AlMCM-48 Molecular Sieves.

Abstract

Employing electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopy, five Mn(II) species are found in three kinds of Mn-containing MCM-48 materials: ion-exchanged Mn−MCM-48, synthesized MnMCM-48, and synthesized MnMCM-48(Ca) with subsequent CaCl2 exchange. Mn(II) species I with a well-resolved sextet centered at g = 2.00 has distorted octahedral symmetry and is observed in hydrated ion-exchanged Mn−MCM-48 and in synthesized calcined MnMCM-48. Mn(II) species II with a group of single peaks between g = 11.32 and 2.62 with possible distorted tetrahedral symmetry and a significant zero field contribution is observed in dehydrated Mn−MCM-48 and in MnMCM-48. Mn(II) species III with a symmetric line at g = 2.00 and a line width around 410 G is assigned to tetrahedral symmetry and is observed in MnMCM-48(Ca) and in MnAlMCM-48(Ca). Mn(II) species IV with a sextet centered from 4.11 to 4.34 also has distorted octahedral symmetry and is obtained in partially dehydrated Mn−MCM-48 and Mn−AlM...