1H and 13C NMR spectra, structure and physicochemical features of phenyl acridine-9-carboxylates and 10-methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulphonates - alkyl substituted in the phenyl fragment

The H-1 and C-13 NMR spectra of twelve phenyl acridine-9-carboxylates - alkyl-substituted in the phenyl fragment - and their 10-methyl-9-(phenoxycarbonyl)acridinium salts dissolved in CD3CN, CD3OD, CDCl3 and DMSO-d(6) were recorded in order to examine the influence of the structure of these compounds and the properties of the solvents on chemical shifts and H-1-H-1 coupling constants. Experimental data were compared with H-1 and C-13 chemical shifts predicted at the GIAO/DFT level of theory for DFT(B3LYP)/6-31G** optimised geometries of molecules, as well as with values of H-1 chemical shifts and H-1-H-1 coupling constants, estimated using ACD/HNMR database software to ensure that the assignment was correct. To investigate the relations between chemical shifts and selected structural or physicochemical characteristics of the target compounds, the values of several of these parameters were determined at the OFT or HE levels of theory. The HOMO and LUMO energies obtained at the HF level yielded the ionisation potentials and electron affinities of molecules. The DFT method provided atomic partial charges, dipole moments, LCAO coefficients of p(z) LUMO of selected C atoms, and angles reflecting characteristic structural features of the compounds. It was found that the experimentally determined H-1 and C-13 chemical shifts of certain atoms relate to the predicted dipole moments, the angles between the acridine and phenyl moieties, and the LCAO coefficients of the p(z) LUMO of the C atoms believed to participate in the initial step of the oxidation of the target compounds. The spectral and physicochemical characteristics of the target compounds were investigated in the context of their chemiluminogenic ability. (c) 2010 Elsevier B.V. All rights reserved.