title: Hydrogen bonding and coordination bonding in the electronically excited states of Cu2(L)2 (L=5-(4-pyridyl)tetrazole)MeOH: a TDDFT study.
abstract: The luminescent metal organic framework (MOF), Cu2(L)2·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 S1 and S0, 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.
authors.affiliation: State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, PR China.
authors.forename: Yanfang
authors.initials: Y
authors.lastname: Meng
authors.forename: Chunqing
authors.initials: C
authors.lastname: Zhang
authors.forename: Min
authors.initials: M
authors.lastname: Ji
authors.forename: Ce
authors.initials: C
authors.lastname: Hao
authors.forename: Jieshan
authors.initials: J
authors.lastname: Qiu
mesh_terms: D003300:Copper / Q000737:chemistry*; D004583:Electrons; D006860:Hydrogen Bonding; D049408:Luminescent Agents / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D013777:Tetrazoles / Q000737:chemistry*
chemical_list: D049408:Luminescent Agents; D009942:Organometallic Compounds; D013777:Tetrazoles; D003300:Copper; D000432:Methanol; C003260:5-(3-pyridyl)tetrazole