Chemiluminogenic features of 10-methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulfonates alkyl substituted at the benzene ring in aqueous media

10-Methyl-9-(phenoxycarbonyl)acridinium trifluoromethanesulfonates bearing alkyl substituents at the benzene ring were synthesized, purified, and identified. In the reaction with OOH(-) in basic aqueous media, the cations of the compounds investigated were converted to electronically excited 10-methyl-9-acridinone, whose relaxation was accompanied by chemiluminescence (CL). The kinetic constants of CL decay, relative efficiencies of light emission, chemiluminescence quantum yields, and resistance toward alkaline hydrolysis were determined experimentally under various conditions. The mechanism of CL generation is considered on the basis of thermodynamic and kinetic parameters of the reaction steps predicted at the DFT level of theory. The chemiluminescence efficiency is the result of competition of the electrophilic center at C(9) between nucleophilic substitution by OOH(-) or OH(-) and the ability of the intermediates thus formed to decompose to electronically excited 10-methyl-9-acridinone. Identification of stable and intermediate reaction products corroborated the suggested reaction scheme. The results obtained, particularly the dependency of the "usefulness" parameter, which takes into account the CL quantum yield and the susceptibility to hydrolysis, on the cavity volume of the entity removed during oxidation, form a convenient framework within which to rationally design chemiluminescent 10-methyl-9-(phenoxycarbonyl)acridinium cations.     

Vibrational spectra of phenyl acridine-9-carboxylates and their 10-methylated cations: A theoretical and experimental study

Infrared spectra of phenyl acridine-9-carboxylates and their 10-methylated cationic derivatives were recorded and discussed. Experimental data were compared with theoretically predicted transitions at the DFT level of theory (using the B3LYP functional and 6-31G** basis set) for optimized geometries of molecules. Substitution influences the values of the wavenumbers of characteristic stretching and bending modes, i.e. those corresponding to ester groups and fragments of molecules containing a heterocyclic nitrogen atom. The experimentally determined transitions of selected groups of atoms correlate well with the theoretically predicted values. Interdependences among some theoretically derived physicochemical features of the compounds and IR frequencies of selected bands are also discussed.     

1H, 13C and 77Se NMR spectra of substituted selenoanisoles

The ¹H, ¹³C and ⁷⁷Se chemical shifts and the ¹J[C(Me)H(Me)], ^1.2J(SeC) and ²J(SeH) coupling constants in 14 para- or meta-substituted selenoanisoles, R? C₆H₄? Se? CH₃, have been measured and the dependence of these parameters on the electronic effects of the substituent R is discussed. A significant (up to 6 ppm) deviation from additivity of the substituent influence on the shielding of the ¹³C ring carbons has been found.     

IR, 1H NMR and 13C NMR spectra of isomeric 1-aryl-4-methyl-3- and-5-pyrazolecarboxylic esters

The IR, ¹H and ¹³C NMR spectra of six esters of 1-aryl-4-methyl-3- and 5-pyrazolecarboxylic acids are reported. On the basis of their spectra the 3- or 5-position of the substituent in such structural isomeric pairs can be established without recourse to the spectrum of the other member of the pair. The spectral data also give information on the conformation, which depends on the relative position and size of the hetero ring substituents.     

Spectral features of substituted 9-(phenoxycarbonyl)-acridines and their protonated and methylated cation derivatives

The long-wavelength absorption of eight 9-(phenoxycarbonyl)-acridines and the 10-H-9-(phenoxycarbonyl)-acridinium and 10-methyl-9-(phenoxycarbonyl)-acridinium cations derived from them, substituted with an alkyl or trifluoroalkyl group at the benzene ring, occurs above 300 nm as the superposition of four bands. Three of these bands occupy comparable positions (expressed in nm) in all the compounds; the fourth one, however, changes position, appearing in neutral molecules as a long-wavelength shoulder below 400 nm, but in cations as an almost separate band above 400 nm. The weak fluorescence resulting from excitation within the long-wavelength absorption band is red-shifted relative to absorption, such that Stokes shifts are similar for both neutral molecules and cations. Stokes shifts tend to increase with the orientational polarisability of a medium. Computations predict that long-wavelength electronic transitions are accompanied by structural changes in molecules. They also indicate that such transitions are followed by roughly uniform electron density changes in whole molecules accompanied by small changes in their dipole moments, which accounts for the weak absorption in the long-wavelength region. The predicted radiative and non-radiative deactivation rate constants suggest the occurrence of efficient spin-orbital coupling in the molecules investigated, which is the cause of the relatively low fluorescence quantum yields. Apart from the cognitive significance of these investigations, the results demonstrate that absorption of radiation by 10-methyl-9-(phenoxycarbonyl)-acridinium cations above 400 nm may influence their chemiluminescence output.     

13C and proton NMR spectra of 2(1H)pyrazinones

¹³C and proton NMR spectra data are given for eleven 2(1H)pyraziones. Assignments of chemical shifts were made by methods which included: deuterium exchange with certain protons of 3-alkyl substituents; change of chemical shifts of certain carbon atoms with change in pH; the use of long-range coupling constants for ¹³C to protons; and various correlations among assigned spectra.     

Automated structure verification based on a combination of 1D (1)H NMR and 2D (1)H - (13)C HSQC spectra

A method for structure validation based on the simultaneous analysis of a 1D (1)H NMR and 2D (1)H - (13)C single-bond correlation spectrum such as HSQC or HMQC is presented here. When compared with the validation of a structure by a 1D (1)H NMR spectrum alone, the advantage of including a 2D HSQC spectrum in structure validation is that it adds not only the information of (13)C shifts, but also which proton shifts they are directly coupled to, and an indication of which methylene protons are diastereotopic. The lack of corresponding peaks in the 2D spectrum that appear in the 1D (1)H spectrum, also gives a clear picture of which protons are attached to heteroatoms. For all these benefits, combined NMR verification was expected and found by all metrics to be superior to validation by 1D (1)H NMR alone. Using multiple real-life data sets of chemical structures and the corresponding 1D and 2D data, it was possible to unambiguously identify at least 90% of the correct structures. As part of this test, challenging incorrect structures, mostly regioisomers, were also matched with each spectrum set. For these incorrect structures, the false positive rate was observed as low as 6%.     

1H and 13C NMR data for C-6 substituted 3-azabicyclo[3.3.1]nonane-1-carboxylates

The 1H and 13C NMR spectra of 3-azabicyclo[3.3.1]nonanes with various oxygenated substituents at C-6 were assigned using 1D (DEPT) and 2D (COSY, HSQC, HMBC, NOESY) experiments. Close examination of this NMR data details the effects of substitution and stereochemistry at C-6 in these compounds.