Theoretical and experimental investigation of the structural and spectroscopic properties of coumarin 343 fluoroionophores

Abstract

A joint theoretical-experimental investigation has been carried out to unravel the details of the complexation of cations by fluoroionophores based on coumarin 343 and to interpret the modifications in the ligand and also in the coumarin structural, electronic, magnetic, and vibrational properties. It is confirmed that C343-dea (1) complexes the cations by both the lactone and the amide oxygen atoms whereas for C343-crown (2) and C343-dibenzocrown (3), the cations are complexed by the oxygen atoms of the lactone as well as those of the crown ligand. These complexations induce geometric modifications, which are delocalized over the coumarin backbone and are related to electronic reorganizations that modify the spectroscopic signatures. This paper analyzes these signatures and shows how they are related as well as how they can be used to monitor the complexation process. Upon complexation, the UV-visible absorption spectra display a bathochromic shift of the most intense electronic transition; this shift is generally larger for the most flexible compound 1 as well as when complexing divalent cations. NMR spectra bear many signatures of the complexation, of which the most remarkable ones are the large shielding of C(1) and the large deshieldings of C(9) and C(16). Additional makers of complexation are highlighted in the IR vibrational spectra, in particular the bands associated with the lactone and amide CO vibrations, which are downshifted when the corresponding CO is involved in the complexation mode and, otherwise, upshifted. A high degree of consistency characterizes the different geometrical, electronic, magnetic, and vibrational signatures, which substantiates the assignment of the modes of complexation in 1-3. In addition, the agreement between the experimental data and the theoretical values is rather satisfactory, in that it at least enables us to interpret the spectral signatures.

Sensing mechanism for a fluoride chemosensor: invalidity of excited-state proton transfer mechanism

“…3. The B3LYP function with 6-311+G(2d,p) basis set, which has been proven appropriate for calculating 1 H chemical shifts, 40,41 was used to calculate the 1 H NMR spectra. For DBM, the signals at d = 8.38, 7.75, and 7.45 ppm were assigned to protons H1, H2, and H3, respectively.…”

Photophysical Properties of Self-Assembled Multinuclear Platinum Metallacycles with Different Conformational Geometries

“…31−35 To obtain a good description of the electron correlation in the excitation processes, the TDDFT method with the cam-B3LYP functional was adopted to investigate the excited states of these supramolecules. 12,47,48 All excited-state calculations were performed using Gaussian 09, 49 and solvent effects were included using the integral equation formalism (IEF) version of the polarizable continuum model (PCM) with the dielectric constant of dichloromethane (ε = 8.93). Throughout the ground-state optimizations and excited-state studies, the SVP basis set was chosen for nonmetallic elements and the def-TZVP and pseudopotential def-ecp basis sets were selected for platinum atoms.…”

Nonlinear Optical Molecular Switches for Alkali Ion Identification

“…Complexing the big Cs + atom leads to a small hypsochromic shift of the S 0 → S 1 transition (7 nm or 0.03 eV) whereas going towards smaller cations, this shift increases up to 18 nm (0.11 eV), consistently with the increase of the BLA along the vinylic linker (Table 1). Note that this hypsochromic shift goes in the opposite direction to what was observed and calculated for coumarin 343 fluoroionophores [32]. The effect of the cation size on the oscillator strengths is negligible.…”