Synthesis and spectral properties of fluorescent dyes based on 4-styryl-1,8-naphthalimide

Abstract

The paper reports on synthesis and spectroscopic study of novel N butyl 4 styryl 1,8 naphthal imide dyes bearing methoxy (1), dimethoxy (2), and dimethylamino (3) groups in the styryl frag ment. It is shown that all synthesized compounds demonstrate positive solvatochromism, high values of Stokes shift in polar solvents, and fluorescence in the long wavelength part of visible range. These facts indicate a potential application of these compounds as fluorescent dyes in the biochem istry. The changes in the dipole moments of the molecules caused by excitation were estimated using Lippert-Mataga equation. The obtained results could be assigned to the formation of the excited states with intramolecular charge transfer. The formation of the twisted states with charge transfer was suggested in the case of compound 3, while the fluorescence quantum yield was significantly reduced in polar protic solvents.

Combined Theoretical and Experimental Study on Intramolecular Charge Transfer Processes in Star-Shaped Conjugated Molecules

“…The change in the dipole moment upon the excitation, ∆μ = μE -μG, is comparable to other compounds in which ITC processes have been reported such as 4-styryl-1,8-naphthalimides, 2,4,6-tri(5aryl-2-thienyl)pyrimidines and boradiazaindacenes, among others. [67][68][69] As expected, ∆μ is especially high in compound 2 and it can be associated to a strong deformation of the excited state.…”

“…These geometric distortions upon excitation should lead to modifications in the dipole moment of the molecule. The Lippert–Mataga equation − was employed to study the influence of solvent on the emission spectra and the change in the dipole moment upon excitation: Here Δν is the Stokes shift (in cm –1 ); ν ab and ν em are the wavenumbers corresponding to spectral maxima in absorption and fluorescence spectra, respectively (in cm –1 ); μ E and μ G are the dipole moments of the compound in solution in excited and ground states, respectively (in D = 1 × 10 –18 cm 5/2 g 1/2 s –1 ); h is the Planck constant ( h = 6.626 × 10 –27 erg s); c is the speed of light in vacuum ( c = 2.998 × 10 10 cm s –1 ); a is the effective radius of Onsager cavity (in cm); and Δ f is the Lippert–Mataga solvent polarity parameter. , Figure shows the dependence of the Stokes shift versus Δf and Table collects the value of the parameters employed for the fitting of the Lippert–Mataga equation. The change in the dipole moment upon the excitation, Δμ = μ E – μ G , is comparable to other compounds in which ITC processes have been reported such as 4-styryl-1,8-naphthalimides, 2,4,6-tri­(5-aryl-2-thienyl)­pyrimidines and boradiazaindacenes, among others. − As expected, Δμ is especially high in compound 2 , and it can be associated with a strong deformation of the excited state.…”

“…1/2 s −1 ); h is the Planck constant (h = 6.626 × 10 −27 erg s); c is the speed of light in vacuum (c = 2.998 × 10 10 cm s −1 ); a is the effective radius of Onsager cavity (in cm); and Δf is the Lippert−Mataga solvent polarity parameter 66,67. Figure 7 shows the dependence of the Stokes shift versus Δf and Table 4 collects the value of the parameters employed for the fitting of the Lippert−Mataga equation.…”

A novel bacteriochlorin–styrylnaphthalimide conjugate for simultaneous photodynamic therapy and fluorescence imaging

“…[35][36][37] Because of its intense fluorescence, large Stokes shifts along with the relative ease of synthetic operations for targeted modification of the molecular structure, these types of compounds have found application in the construction of fluorescent chemosensors for biologically relevant cations and anions, [38][39][40] labels or probes for proteins, cells, lysosomes and other acidic organelles. [41][42][43] In our recent papers, [44][45][46] we have described photophysical properties of naphthalimides containing a substituted styryl fragment as an electron releasing group at the 4 th position of a naphthalene ring. It has been found that the presence of the 4-(N,N-dimethylamino)styryl group extends the p-system of the parent chromophore and results in the long wavelength intramolecular charge transfer (ICT) absorption and emission, which is preferable for fluorescence imaging.…”

Fluorescent photochromic complex of 1,8-naphthalimide derivative and benzopyrane containing benzo-18-crown-6 ether

“…22 Photochromic E,Z-isomerization in 4-styryl-1,8-naphthalimides does not significantly affect their fluorescent properties. 23,24 In the two photochromic spirooxazines-naphthalimides, the imide group of naphthalimide unit gives strong electron-withdrawing effect favoring the long-lived merocyanine in the dark and good colorability in solution. 25 Remarkably, their open merocyanine forms exhibit significantly long lifetimes, almost three magnitudes longer than that of unsubstituted spironaphthoxazine.…”