N. M. Shishlov

Color centers in poly(arylenesulfophthalides) and the ground state of Müller's hydrocarbon molecule

Published data on the properties of Müllers hydrocarbon are analyzed. The total energies of several hydrocarbon biradicals withp-phenylene bridges, including Thieles, Chichibabins, and Müllers hydrocarbons in the singlet and triplet states were calculated by the AM1 and PM3 semiempirical quantum-chemical methods. Contrary to popular opinion, our calculations revealed that the Müllers hydrocarbon molecule has a triplet rather than singlet ground state. The results obtained make it possible to explain the fact that quinoid color centers do not form in the course of reduction of poly(terphenylsulfophthalide). The calculated parameters of electronic spectra for singlet states of some related biradicals are reported.

On the possibility of single-electron transfer during alkaline hydrolysis of sulfophthalides

The previously observed generation of radical products during the alkaline hydrolysis of diphenylsulfophthalide (DPSP) and polydiphenylenesulfophthalide in dimethyl sulfoxide (DMSO) is indicative of the involvement of single-electron transfer (SET) in thses processes. The possibility of SET from the hydroxide ion (HI) to the sulfophthalide molecule is determined by the ratio between the ionization potential (IP) of the HI and electron affinity (EA) of the sulfophthalide. According to B3LYP/6-311+G(d,p) calculations for DPSP, EAver = 0.06 eV and EAad = 0.58 eV, whereas EAeff = 2.13 eV (with consideration of the C-O bond rupture in the sulfophthalide cycle). Such a value of the electron affinity cannot ensure SET from the HI, the ionization potential of which in DMSO reaches ∼5.25 eV. The EA of the carbocation formed from DPSP is 6.44 eV as calculated in the same approximation. A mode of SET from the HI to the carbocation intermediate formed during DPSP heterolysis in DMSO is proposed. Two possible modifications of the electron donor are considered. The possibility of occurrence of SET from the dimsyl ion and HI-DMSO complex is evaluated using the G3B3 method. The ionization potential of the dimsyl ion in DMSO is almost 1 eV lower than the IP of the HI, which makes the former a preferential donor in comparison with the HI. The ionization potential of the weak HI-DMSO complex even exceeds the IP of the HI; i.e., complexation does not improve the electron-donor properties of the hydroxide ion.

Formation of mono-, bi-, and polyradicals upon reduction of poly(arylenesulfophthalides) by metallic lithium

The reduction of poly(biphenylenesulfophthalide) (1), poly(fluorenylenesulfophthalide) (2), and poly(terphenylenesulfophthalide) (3) by metallic lithium in DMSO was studied using UV-visible and ESR spectroscopies. The reduction of compounds 1 and 2 affords blue diamagnetic color centers with absorption bands at 568 and 350 nm (shoulder) for 1 and at 576 and 360 nm (shoulder) for 2. The color centers were attributed to quinoid structures of the Chichibabins hydrocarbon type, being biradicals in the ground singlet state. The spectra of compounds 1 and 2 also exhibit weak absorption bands at ∼420 nm, which are assigned to monoradicals of the triarylmethyl type. The reduction of compound 3, for which the formation of quinoid structures is energetically unfavorable, leads to polyradicals of the triarylmethyl type with a high content (∼100%) of unpaired electrons in the main polymer chain. These radicals are characterized by absorption bands at 430 nm (allowed transition) and 638 nm (forbidden transition). The paramagnetic centers in all polymers under study give singlet lines with g = 2.0028 and ΔH ∼ 10 Oe in the ESR spectra. The color centers and radicals of the triarylmethyl type observed for the poly(arylenesulfophthalides) under study are assumed to be formed upon the dissociative electron transfer from lithium to the sulfophthalide cycles of the polymeric molecules. The PM3 calculations show a high electron affinity of the sulfophthalide cycle and a higher propensity of the fluorenyl bridge to form quinoid structures than that of the biphenyl bridge.

Formation of color centers and paramagnetic species by alkaline hydrolysis of polydiphenylenesulfophthalide

Blue color centers (CC) (an intense absorption band (AB) at 566 nm and a weaker AB at 350 nm) and paramagnetic species (PMS) that give an ESR singlet withg=2.0028 and δH=10 Oe are formed by the treatment of a DMSO solution of polydiphenylenesulfophthalide with an excess of LiOH. The formation of blue CC is accompanied by a decrease in the intensity of the absorption band of the phenyl groups of the polymer at 270 nm. The blue CC were attributed to quinoid structures like the Chichibabin hydrocarbon. The long-wave absorption at 650–800 nm was assigned to the regions of quinoid-benzoid conjugation. The color centers and PMS were also observed when the polymer was hydrolyzed in cyclohexanone; however, in this case, the reaction was accompanied by polymer aggregation. The electronic spectrum of the Chichibabin hydrocarbon was calculated by the PM3 method. The identity of CC formed by alkaline hydrolysis and appearing in the polymer—aniline—cyclohexanone system was shown. The absence of “quinoid” CC for polyterphenyl sulfophthalide was explained by the energetically unfavorable singlet state for structures similar to the Müller hydrocarbon.

IR spectroscopic manifestations of hydration of poly(diphenyl sulfophthalide) during its storage

IR spectroscopy measurements show that films of poly(diphenyl sulfophthalide) (PDSP), a cardo polymer, interact with atmospheric moisture during storage at room conditions. A total of 15 absorption bands were isolated in spectra of PDSP hydrated during storage, which belong to sorbed water and hydrolysis products. A number of absorption bands (within 1500–1800 cm−1 and 980–1100 cm−1) were obtained by subtracting the spectrum of the film after heating from that of the initial hydrated film. At least six individual bands in the region of the O-H bond stretching vibration were isolated by decomposing a broad complex band (3700–2000 cm−1) into Gaussian components. The isolated bands were tentatively assigned based on the available literature data and quantum-chemical calculations of the characteristics of a number of complexes of a diphenyl sulfophthalide model compound with water molecules. The IR spectra and energies of the hydrogen bonds formed were calculated at the B3LYP/6-311G(d, p) level. In particular, the absorption bands at 1010 and 1079 cm−1 were assigned to the symmetric stretching vibrations of the S=O bonds in the −SO3− anion, the 1062-cm−1 absorption band, to ν(C-OH), and the absorption bands at 3646, 3586, and 3475 cm−1, to complexes of water with sulfophthalide cycles of the polymer. After a long storage, PDSP largely transforms into a polymeric oxonium salt, and its spectrum becomes similar to that of a polymeric salt prepared by alkaline hydrolysis. A general mechanism of the interaction of PDSP with water is proposed, according to which the hydrolysis of the sulfophthalide cycles (SPC) by sorbed water yields new hydrophilic groups, sulfoacid, and hydroxyl groups. A further sorption of water by the sulfoacid results in its ionization and the formation of various hydroxonium forms. Sorption and hydrolysis are reversible processes: water is desorbed and the SPC is recovered when the polymer is heated to 100–150°C, as can be judged from an increase in the intensity of the S=O bond vibrations of the sulfophthalide cycle at 1352 and 1192 cm−1. The possibility of using strongly hydrated PDSP for manufacturing proton-conducting membranes is discussed.

Kinetics of formation and thermal decomposition of 1,1-diethoxyethane hydrotrioxide

Conclusions1.The dependence of the yield of hydrotrioxide during the ozonation of 1,1-diethoxy-ethane on temperature and degree of conversion shows that when the process has progressed to a great extent, ozone enters into reaction with the hydrotrioxide.2.The thermal decomposition of 1,1-diethoxyethane hydrotrioxide proceeds mainly by a nonradical mechanism; the fraction of radical decomopsition, measured by the acceptors method, is 1.2%.3.The first discovery was made of the fact that the thermal decomposition of acetal hydrotrioxides is accompanied by chemiluminescence in the IR region.

Sulfophthalide cycle cleavage and formation of fluorenyl structures upon poly(diphenylene sulfophthalide) thermolysis

Thermolysis of poly(diphenylene sulfophthalide) (PDSP) in the temperature range from 100 to 500 °C was studied by IR and UV-Vis spectroscopy and thermogravimetric analysis. A series of absorption bands in the IR spectrum of PDSP were assigned on the basis of the theoretical calculations of the IR spectrum of diphenyl sulfophthalide used as a model compound, in particular, νas(S=O) = 1352 cm−1, νs(S=O) = 1196 cm−1, ν(C-O) ∼ 920 cm−1, ν(S-O) = 824 cm−1, and δ(SO2) = 576 cm−1. The sulfophthalide cycle (SPC) in PDSP decomposes at the thermolysis temperatures in a range of 260–400 °C. An analysis of the IR spectra of the thermolyzate and the quantum chemical calculations of the IR spectra of the model compounds confirmed the predominant formation of fluorenyl structures in the thermolyzed polymer. The changes in the UV-Vis spectra observed upon the thermolysis of thin films of PDSP (the hypsochromic shift of the long-wavelength absorption band from 271 to 263 nm and the appearance a shoulder at ∼310 nm) and the results of TD-DFT calculations of the UV-Vis spectra of the model compounds are consistent with the hypothesis about the formation of fluorenyl structures. The general scheme of PDSP thermolysis at 260–400 °C was proposed in which the major process is the formation of fluorenyl fragments in macromolecules of the polymer due to the intramolecular ring closure in biradicals formed by the SPC cleavage.

Formation of triphenylmethyl radicals upon alkaline hydrolysis of diphenyl sulfophthalide

Triphenylmethyl radicals (TPMR) with ano-positioned sulfonate group are generated by alkaline hydrolysis of diphenyl sulfophthalide in DMSO. Electronic and ESR spectra of these radicals are characterized. It is suggested that the radicals result from one-electron transfer reactions. Triarylmethyl radicals are also formed in alkaline hydrolysis of polyarylenesulfophthalides.

COLOR REACTIONS OF POLYARYLENESULFOPHTHALIDES IN ANILINE-CYCLOHEXANONE MIXTURES IN AIR

Slow color reactions occur when some polyarylenesulfophthalides are dissolved in an aniline—cyclohexanone mixture; these reactions involve generation of triarylmethyl type radicals that were characterized by ESR and UV spectroscopy.

Formation of triphenylmethyl radicals in the thermolysis of polydiphenylenesulfophthalide and polytriphenylcarbinol

Triphenylmethyl radicals are formed in the thermolysis of polytriphenylcarbinol and polydiphenylenesulfophthalide, which give rise to ESR singlets with poorly resolved hyperfine structure and two bands in the electronic absorption spectra.