Indexed by:期刊论文

Date of Publication:2013-05-15

Journal:SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY

Included Journals:SCIE、EI、PubMed

Volume:109

Page Number:14-22

ISSN No.:1386-1425

Key Words:Luminescent MOFs; Hydrogen bonding; Coordination bonding; Excited states

Abstract:The luminescent metal organic framework (MOF), Cu-2(L)(2)center dot MeOH (L = 5-(4-pyridyl)tetrazole), was studied using time-dependent density functional theory (TDDFT). A combination of frontier molecular orbitals and electronic configuration analysis revealed that the emission mechanism was a ligand to metal charge transition (LMCT) rather than a metal to ligand charge transfer (MLCT). Hydrogen bonding significantly changed the nature of the frontier orbital and the luminescence. Electronic transition energies predicted that the hydrogen bonding in excited state would become weaker with an electronic spectral blue-shift. The bond lengths, frequencies, and binding energies indicated weakening of the hydrogen bonding in the excited state, which can affect emissions in two ways, including: (i) a decrease in the electronic coupling between methanol and the motif and suppressing the occurrence of the photo-induced electron transfer (PET); and (ii) increasing the energy gap between S-1 and S-0, leading to radiative transition. Coordination bonding was also investigated in the excited state through bond lengths, frequencies, and bond orders. Coordination bonds were found to become stronger in the excited state leading to an enhancement of the luminescence. (C) 2013 Elsevier B.V. All rights reserved.