title: Computational design of zinc-ion-responsive two-photon fluorescent probes with conjugated multi-structures.
abstract: A series of conjugated multi-structured fluorescent probe molecules based on a salen ligand were designed and investigated in dimethyl sulfoxide solvent using a quantum-chemical method. The results indicate that the one-photon absorption and fluorescence emission spectra (λ (O) and λ (EM)) of these molecules generally show redshifts (of 23.1-74.5 and 22.7-116.6 nm, respectively) upon the coordination of the molecules to Zn(2+). Large Stokes shifts (1511.2-11744.1 cm(-1)) were found for the molecules, meaning that interference between λ (O) and λ (EM) can be avoided for these molecules. The two-photon absorption spectra of the molecules usually present blueshifts, but the two-photon absorption cross-section (δ) greatly increases (by 221.5-868.0 GM) upon the coordination of the molecules with Zn(2+). Most of the molecules show strong two-photon absorption peaks in the range 678.2-824.4 nm, i.e., in the near-infrared region. In a word, the expanded π-conjugated frameworks of these molecules lead to redshifted λ (O) and λ (EM) and enhanced δ values. Moreover, (L-phenyl)​2 and (L-phenyl-ethynyl)2 are the most suitable of the multi-structured molecules examined in this work for use as two-photon fluorescent probes for zinc ion detection in vivo. Graphical Abstract Scheme of the calculated transition energies (E0k and E0n) and the transition dipole moments (M0k and Mkn). NTO 109, NTO 197 and NTO 228 of Zn(L-phenyl-ethynyl), Zn2(L-phenyl-ethynyl)2 and Zn3(L-phenyl)3 for one-photon absorption, respectively.
authors.affiliation: School of Mathematics and Physics, Changzhou University, Changzhou, 213164, People's Republic of China.|State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Hangzhou, People's Republic of China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Huang
authors.affiliation: School of Petrochemical Engineering, Changzhou University, Changzhou, 213164, People's Republic of China. yang.baozhu@yahoo.com.
authors.forename: Bao-Zhu
authors.initials: BZ
authors.lastname: Yang
authors.affiliation: School of Mathematics and Physics, Changzhou University, Changzhou, 213164, People's Republic of China.|State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Hangzhou, People's Republic of China.
authors.forename: Xing-Fang
authors.initials: XF
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, 130023, People's Republic of China.
authors.forename: Ai-Min
authors.initials: AM
authors.lastname: Ren
keywords: Fluorescent probe; Multi-structure; Near-infrared region; Two-photon absorption; Zinc ion