Electron transfer in mesoporous (A1)-MCM-41 hosts [thesis]

Hongxian Han
Various kinds of electron donors, acceptors and D-B-A dyads have been assembled into the channels of the mesoporous (Al)-MCM-41 hosts. The chemistry of these organic molecules in the (Al)-MCM-41 hosts and the redox properties of the (Al)-MCM-41 hosts have been extensively studied in this work. It is found that Al-MCM-41 materials feature both electron donor sites and electron acceptor sites, while Si-MCM-41 has no (or rather weak) redox sites at room temperature. The electron donor and acceptor
more » ... sites are assigned to the negatively charged oxygen bonded to the extra-framework Al (oxide ions) and the Lewis acid sites, respectively. The oxidation potential of the Al-MCM-41 is determined to be in the range: -1.0 V :' .S E 0 x (Al-MCM-41) :' .S -0.92 V; while the reduction potential of the Al-MCM-41 is determined to be in the range: 1.18 V :' .S ERect (Al-MCM-41) :' .S 1.34 V. Al-MCM-41 materials are ideal heterogeneous hosts for generating and stabilizing radical species. Radical anions and cations generated via electron transfer with the Al-MCM-41 framework are long-lived in the Al-MCM-41 hosts. The DMN-6B-DCV dyad formed long-lived radical cations of the DMN group which were complexed with the Lewis acid sites (extra-framework Al 3 +) in the Al-MCM-41 hosts after photoirradiation; while the DMN-8B-BQ dyad formed tightly bound "radial anion of the BQ group---Al (extra-framework Al 3 +)" ion pairs which were also longlived. The extra-framework Al also plays an important role in the formation of longlived radical cation or anion of the occluded dyads in the Al-MCM-41 hosts. Electron transfer processes in the Al-MCM-41 hosts largely depend on the molecular assembling conditions, such as the nature of the assembled molecules (e.g., the redox potential, steric effects and adsorption ability), the nature of the hosts (e.g., the Al content in the framework), the pretreatment method (e.g., synthesis procedure, dehydration temperature) and the media (solvent) used for assembling the guest-host systems. 157 s1 tea e 1 ayer.
doi:10.26190/unsworks/9082 fatcat:t5jvpczk65gedkevmz6z2qd52y