Premium
Large Stokes Shifted Far‐Red to NIR‐Emitting D‐π‐A Coumarins: Combined Synthesis, Experimental, and Computational Investigation of Spectroscopic and Non‐Linear Optical Properties
Author(s) -
Avhad Kiran C.,
Patil Dinesh S.,
Gawale Yogesh K.,
Chitrambalam Subramaniyan,
Sreenath Mavila C.,
Joe Issac H.,
Sekar Nagaiyan
Publication year - 2018
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201800063
Subject(s) - hyperpolarizability , solvatochromism , fluorescence , z scan technique , chemistry , molecular physics , stokes shift , materials science , nonlinear optics , thiophene , wavelength , natural bond orbital , acceptor , nonlinear system , polarizability , computational chemistry , optics , density functional theory , molecule , optoelectronics , physics , organic chemistry , quantum mechanics , condensed matter physics
Coumarin based push‐pull fluorophores ( COM‐1 to COM‐5 ) bearing thiophene π‐spacer were synthesized having a donor at 7‐position and acceptor at 3‐position. Increasing the π‐conjugation length shifts their fluorescence maxima to the longer wavelength (600–756 nm). All fluorophores exhibit positive emission solvatochromism, fluorescence lifetime is in the range of 1.31 to 2.18 ns, and are high thermal stability. The nonlinear optical behavior was investigated by calculating the first/second‐order hyperpolarizability using a spectroscopic and computational method wherein, COM‐3 shows higher optical nonlinearity ( μβ CT =987 x 10 −48 e.s.u and μβ 0 =9758 x 10 −48 e.s.u.) in DMF. Third‐order nonlinear optical parameters measured using the Z‐scan method in each closed and open aperture curves. The fluorophores possess the self‐focusing effect and show negative nonlinear absorption coefficient ( β ) and positive nonlinear refractive index ( n ). Among all fluorophores, COM‐5 shows better real part of third‐order susceptibility χ (3) in DMSO (8.58 x 10 −13 e.s.u.). Bond length alternation (BLA), natural bond orbital analysis (NBO), and generalized Mulliken‐Hush (GMH) analysis were studied to give theoretical evidence to the effective charge transfer (CT). Quadratic optical nonlinearity and Z‐scan results show that these coumarin‐based fluorophores can be considered as promising candidates for organic NLOphores in material for nonlinear optics.