Beata Zadykowicz

Chemiluminogenic properties of 10-methyl-9-(phenoxycarbonyl)acridinium cations in organic environments.

The chemiluminogenic (CL) properties of aryl esters of 9-carboxy-10-methylacridinium acid and 9-carboxy-2-methoxy-10-methylacridinium acid (AE), variously substituted in the benzene ring (2-H, 2-CH(3), 2-Cl) were investigated in aliphatic alcohols, acetonitrile, and dimethyl sulfoxide in the presence of hydrogen peroxide and different bases-potassium hydroxide, tetra-n-butylammonium hydroxide, and 1,8-diazabicyclo[5.4.0]undec-7-ene. The dependence of their CL properties (decay rate constants (k(CL)) and relative efficiencies (RE)) on solvent parameters, the nature and concentration of base, as well as H(2)O(2) concentration were investigated. Comparison of the various AE revealed that substituents at the benzene ring strongly influence the reaction kinetics, while 2-OCH(3) substitution of the acridine nucleus is manifested, in general, by a red shift in the emission spectrum and slight increase in CL efficiency. The values of k(CL) depend linearly on polarity and acid-base properties of solvents as well as on concentration of bases (over certain concentration ranges) and demonstrate a nonlinear dependence on H(2)O(2) concentration. RE values depend on solvent polarity and nucleophilicity but are rather weakly dependent on base and oxidant concentrations. The CL properties of the above systems are discussed in the context of their physicochemical features gained from fluorescence spectroscopy, spectrophotometric titration, MS, and HPLC. Electronically excited 10-methyl-9-acridinones are the light-emitting entities in both organic and aqueous environments. It was also found that the tendency for an unwanted side-process, the production of a pseudobase form of AE, to take place was similar in alcoholic and aqueous media, although 2-methoxy ring-substituted derivatives seemed to be less susceptible to this dark-type conversion. On the basis of these results new CL systems are postulated that are more efficient than their aqueous counterparts.

Tautomerism and behavior of 3-hydroxy-2-phenyl-4H-chromen-4-ones (flavonols) and 3,7-dihydroxy-2,8-diphenyl-4H,6H-pyrano[3,2-g]chromene-4,6-diones (diflavonols) in basic media: spectroscopic and computational investigations.

Absorption and emission spectroscopic investigations and computational predictions have shown that neutral molecules of flavonols and diflavonols can exist in the ground and excited states in one or two tautomeric forms stabilized by intramolecular (in aprotic media) or intermolecular (with solvent molecule(s), in protic media) hydrogen bonds. Electronic excitation creates conditions for the transformation of tautomeric forms, accompanied by proton transfer, reflected in fluorescence spectra. Proton transfer is also probable in monoanions of diflavonols in protic media. The OH groups involved in hydrogen bonds exhibit a proton-donating ability characterized by the respective acidity constants. The electronically excited diflavonols are relatively strong acids if they lose one proton. With increasing basicity of the medium, anionic forms occur, which exhibit spectral characteristics and emission abilities different from those of neutral molecules. These features open up possibilities for the analytical use of these compounds as spectral probes sensitive to the properties of liquid phases--from neutral to strongly basic. The less intensively studied diflavonols seem to be more promising than flavonols for these purposes, since they are more lipophilic, polarizable, polar, and sensitive to basic features of the environment.

Computational prediction of the pattern of thermal gravimetry data for the thermal decomposition of calcium oxalate monohydrate

The multistep decomposition of CaC2O4·H2O in the gaseous phase was explored at the MP2/cc-pVDZ level of theory. As a result, the structure and energy of the entities occurring at stationary points along the reaction pathway were determined. Statistical thermodynamics routines were used to obtain thermal energies/enthalpies and entropies. The results demonstrated the consecutive release of H2O, CO and CO2 from the substrate with increasing temperature. Moreover, the application of thermodynamic and kinetic characteristics to relevant phenomenological relationships enabled the decomposition pattern in equilibrium and non-equilibrium conditions to be predicted. The forecast patterns qualitatively match the experimental thermal gravimetry data. This study supplies much important information on the molecular changes taking place in a stoichiometric unit of calcium oxalate monohydrate during continuous heating

Structure, tautomerism, and features of 1-(5-acetyl-2,4-dihydroxyphenyl)-3-(furan-2-yl)prop-2-en-1-one (FC) and 1,1′-(4,6-dihydroxybenzene-1,3-diyl)bis[3-(furan-2-yl)prop-2-en-1-one] (FDC)

Quantum chemistry studies of various tautomeric/rotameric forms of the furanyl analogues of acetyl dihydroxychalcone (FC) and dihydroxydichalcone (FDC) have shown that the thermodynamically most stable molecules are planar. In the crystalline solid phase, both molecules are more (FDC) or less (FC) non-planar. Two relatively strong intramolecular H-bonds, whose existence is evidenced by X-ray, computational, and spectral investigations, stabilize the planar geometry and influence the features of the lowest energy tautomers/rotamers of both compounds. Extending to the visible region, the electronic absorption of FC and FDC is accompanied by an intramolecular electron density shift, a property that could have analytical implications.

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 1H and 13C 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-d6 were recorded in order to examine the influence of the structure of these compounds and the properties of the solvents on chemical shifts and 1H-(1)H coupling constants. Experimental data were compared with 1H and 13C 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 1H chemical shifts and 1H-(1)H 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 DFT or HF 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 pz LUMO of selected C atoms, and angles reflecting characteristic structural features of the compounds. It was found that the experimentally determined 1H and 13C 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 pz 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.

Structure, formation, thermodynamics and interactions in 9-carboxy-10-methylacridinium-based molecular systems

9-Carboxy-10-methylacridinium chloride and trifluoromethanesulfonate, the parent compounds for a wide range of chemiluminogenic salts of practical importance, were synthesized and thoroughly investigated to address problems concerning structural and thermodynamical issues of these cognitively interesting molecular systems. Under various conditions of crystallization, the title salts disclosed three types of crystals: one built from the monomeric form of cations and two containing homoconjugated cations. The title compounds made the first described derivatives of acridine, expressing homoconjugated cationic forms, both in crystalline solid and gaseous phases. The monocrystals were characterized, employing X-ray crystallography and spectroscopic methods such as MALDI-TOF MS, ESI-QTOF MS, NMR and UV-Vis. X-ray crystallography studies revealed the occurrence of the three different molecular architectures, in which not only the counter ions and stoichiometry are different, but also the space group and number of molecules in the unit cell. The energetics and intermolecular interactions occurring within the crystals were explored, applying crystal lattice energy calculations and Hirshfeld surface analysis. In order to elucidate the thermodynamics and origin of the experimentally revealed forms, computations based on the density functional theory were performed, assuming vapour and liquid phases.

2-Meth­oxy-9-phenoxy­acridine

The molecules in the crystal structure of the title compound, C20H15NO2, form inversion dimers connected through the C—H⋯N and π–π interactions. These dimers are further linked by C—H⋯π interactions. The methoxy group is nearly coplanar with the acridine ring system [dihedral angle = 4.5 (1)°], whereas the phenoxy fragment is nearly perpendicular to it [dihedral angle = 85.0 (1)°]. The mean planes of the acridine ring systems are either parallel or inclined at angles of 14.3 (1), 65.4 (1) and 67.3 (1)° in the crystal.

9-Chloro-2,4-dimethoxy­acridinium trifluoro­methane­sulfonate

In the molecular structure of the title compound, C15H13ClNO2 +·CF3SO3 −, the methoxy groups are nearly coplanar with the acridine ring system, making dihedral angles of 0.4 (2) and 5.1 (2)°. Multidirectional π–π contacts between acridine units are observed in the crystal structure. N—H⋯O and C—H⋯O hydrogen bonds link cations and anions, forming a layer structure.

9-(Methyl-sulfan-yl)acridinium trifluoro-methane-sulfonate.

In the crystal structure of the title compound, C14H12NS+·CF3SO3 −, N—H⋯O hydrogen bonds link cations and anions into ion pairs. Inversely oriented ion pairs form stacks through multidirectional π–π interactions among the acridine units. The crystal structure features a network of C—H⋯O interactions among stacks and also long-range electrostatic interactions among ions. In the packing of the molecules, the acridine units are nearly parallel in stacks or inclined at an angle of 33.07 (2)° in the four adjacent stacks with which they interact via weak C—H⋯O interactions. The methylsulfanyl group is twisted through an angle of 60.53 (2)° with respect to the acridine ring.

Lattice energetics and thermochemistry of acridine derivatives and substituted acridinium trifluoromethanesulphonates

The enthalpies and temperatures of melting of eight 9-substituted acridines (alkyl, aryl or alkoxy) (I) and six their 10-methylated-acridinium trifluoromethanesulphonate (II) derivatives were measured by DSC. The enthalpies and temperatures of volatilisation of the first group of compounds were also determined by DSC or obtained by fitting TG curves to the Clausius–Clapeyron relationship. By combining the enthalpies of formation of gaseous acridines or 10-methylacridinium trifluoromethanesulphonate ions, obtained by the DFT method, and the corresponding enthalpies of sublimation and/or crystal lattice enthalpies, the enthalpies of formation of the compounds in the solid phase were predicted. For compounds whose crystal structures are known, experimental enthalpies of sublimation correspond reasonably well to crystal lattice enthalpies predicted theoretically as the sum of electrostatic, dispersive and repulsive interactions. Analysis of crystal lattice enthalpy contributions indicates that dispersive interactions between molecules always predominate in the case of acridine derivatives, whilst the crystal lattices of their quaternary salts are stabilised by electrostatic interactions between ions. Only in the case of 9-bromomethylacridine derivative, which crystallises in the monohydrated form, electrostatic contribution to the crystal lattice energy is significantly higher than in the other investigated acridines.