title: Sensitive and selective PET-based π-expanded phenanthrimidazole luminophore for Zn2+ ion.
abstract: The novel photoinduced electron transfer (PET) chemosensor, 1-(1-(4-methoxyphenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)naphthalen-2-ol [MPPN] and its zinc complex were synthesised and characterized by electronic spectral and Frontier molecular orbital energy analysis. MPPN becomes efficient fluorescent chemosensor upon binding with metal ions and shows a strong preference toward Zn(2+) ion. Density Functional theory (DFT) calculations reveal that luminescence of free MPPN originates from its orbital structure in which two π-orbitals (HOMO and HOMO-1) of the imidazole ring are situated between two π-orbitals (HOMO-2 and LUMO) of the naphthyl fragment. Therefore the absorption and emission processes occur between the two π- orbitals (HOMO-2 and LUMO). The two higher energy imidazole orbitals (HOMO and HOMO-1) serve as quenchers for the excited state of the molecule through nonradiative processes. Upon binding with Zn(2+) ion, MPPN becomes a highly luminescent with λemi - 421 nm. The significant enhancement of luminescence upon binding with Zn(2+) ion is attributed to the stabilization of HOMO-2 and HOMO-1 π-orbitals of imidazole ring upon their engagement in new bonds with Zn(2+) ion. The affinity of MPPN to zinc ion is found to be very high [K = 6 × 10(6) M(-1)] when compared with other metals ions. The nonlinear absorption coefficient γ for MPPN is 1.9 × 10(-12) m/W and 3.9 × 10(-11) m/W for MPPN-Zn complex.
authors: Department of Chemistry, Annamalai University, Annamalainagar, 608 002, Tamilnadu, India, jtchalam2005@yahoo.co.in.
authors: J
authors: J
authors: Jayabharathi
authors: P
authors: P
authors: Ramanathan
authors: V
authors: V
authors: Thanikachalam
authors: A
authors: A
authors: Arunpandiyan
mesh_terms: D004579:Electron Transport; D005456:Fluorescent Dyes / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D049449:Luminescence; D008958:Models, Molecular; D015394:Molecular Structure; D010618:Phenanthrolines / Q000737:chemistry*; D049268:Positron-Emission Tomography; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D015032:Zinc / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D007093:Imidazoles; D010618:Phenanthrolines; D015032:Zinc