Dependence of (35)Cl NQR on hydrogen bonding and temperature in dichlorophenol-aniline charge transfer complexes

The hydrogen-bonded charge transfer complexes of aniline with pi-acceptors (or proton donors) such as 2,5-, 2,6-, 3,4- and 3,5-dichlorophenol were prepared. The (35)Cl nuclear quadrupole resonance (NQR) frequencies of these charge transfer complexes in the temperature range 77-300 K were measured to ascertain the existence or otherwise of a phase transition upon complex formation. Further, the NQR frequency and asymmetry parameter of the electric field gradient at the site of quadrupole nucleus were used to estimate the chemical bond parameters, namely ionic bond, double bond character of the carbon-chlorine(C--Cl) bond and the percentage charge transfer between the donor-acceptor components in charge transfer complexes. The effect of hydrogen bonding and temperature on the charge transfer process is analysed.     

Electronic structure of thiazides studied by 35Cl‐NQR spectroscopy and DFT calculations

NQR frequencies were determined for the ³⁵Cl isotope in a few benzodithiazine derivatives, chlorothiazide (CTZ), hydrochlorothiazide (HCTZ), althiazide (ATZ), trichloromethiazide (TCTZ), benzthiazide (BTZ) and furosemide (FSE), at liquid nitrogen and room temperatures. It was found that changes of the substituent at C‐3 are transferred through a system of coupled rings on to the chlorine atom at C‐6. The substituents occurring in thiazides can be ordered according to increasing electron‐acceptor properties as —CH₂SCH₂Ph < —CH₂SCH₂CH?CH₂ <—CHCl₂. At the liquid nitrogen temperature —CH₂SCH₂Ph and —CH₂SCH₂CH?CH₂ are electron donors, and CHCl₂ is an electron acceptor, whereas at room temperature —CH₂SCH₂Ph is an electron donor and —CH₂SCH₂CH?CH₂ and —CHCl₂ are electron acceptors. The character of the substituent properties is preserved irrespective of whether the system is aromatic or aliphatic. The NQR frequencies and substituents properties are well reproduced by the DFT B3LYP/6–311+G(2d,p) method. The topological properties of the Laplacian of the electron density were analysed within the AIM (atoms in molecules) approach. The changes in the electron density at C‐3 are correlated with the biological activity of the compounds studied. Copyright © 2003 John Wiley & Sons, Ltd.     

Three‐dimensional hydrogen‐bonded structures in the hydrated proton‐transfer salts of isonipecotamide with the dicarboxylic oxalic and adipic acid homologues

The structures of the 1:1 hydrated proton‐transfer compounds of isonipecotamide (piperidine‐4‐carboxamide) with oxalic acid, 4‐carbamoylpiperidinium hydrogen oxalate dihydrate, C₆H₁₃N₂O⁺·C₂HO₄⁻·2H₂O, (I), and with adipic acid, bis(4‐carbamoylpiperidinium) adipate dihydrate, 2C₆H₁₃N₂O⁺·C₆H₈O₄²⁻·2H₂O, (II), are three‐dimensional hydrogen‐bonded constructs involving several different types of enlarged water‐bridged cyclic associations. In the structure of (I), the oxalate monoanions give head‐to‐tail carboxylic acid O—H...O_carboxyl hydrogen‐bonding interactions, forming C(5) chain substructures which extend along a. The isonipecotamide cations also give parallel chain substructures through amide N—H...O hydrogen bonds, the chains being linked across b and down c by alternating water bridges involving both carboxyl and amide O‐atom acceptors and amide and piperidinium N—H...O_carboxyl hydrogen bonds, generating cyclic R₄³(10) and R₃²(11) motifs. In the structure of (II), the asymmetric unit comprises a piperidinium cation, half an adipate dianion, which lies across a crystallographic inversion centre, and a solvent water molecule. In the crystal structure, the two inversion‐related cations are interlinked through the two water molecules, which act as acceptors in dual amide N—H...O_water hydrogen bonds, to give a cyclic R₄²(8) association which is conjoined with an R₄⁴(12) motif. Further N—H...O_water, water O—H...O_amide and piperidinium N—H...O_carboxyl hydrogen bonds give the overall three‐dimensional structure. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen‐bonded structures. The presence of solvent water molecules in these structures is largely responsible for the non‐occurrence of the common hydrogen‐bonded amide–amide dimer, promoting instead various expanded cyclic hydrogen‐bonding motifs.     

Computational study of structures and proton transfer in hydrogen‐bonded ammonia complexes using semiempirical valence‐bond approach

In this study, the seGVB method was implemented for the N H bonding system, specifically for hydrogen‐bonded ammonia complexes, and the model well reproduces the MP2 geometries and energetics. A comparison between the ammonia dimer and water dimer is given from the viewpoint of valance‐bond structures in terms of the calculated bond energies and pair–pair interactions. The linear hydrogen bond is found to be stronger than the bent bonds in both cases, with the difference in energy between the linear and cyclic structures being comparable in both cases although the NH bonds are generally weaker. The energy decomposition clearly demonstrates that the changes in electronic energy are quite different in the two cases due to the presence of an additional lone pair on the water molecule, and it is this effect which leads to the net stabilization of the cyclic structure for the ammonia dimer. Proton‐transfer profiles for hydrogen‐bonded ammonia complexes [NH₂ H NH₂]⁻ and [NH₃ H NH₃]⁺ were calculated. The barrier for proton transfer in [NH₃ H NH₃]⁺ is larger than that in [NH₂ H NH₂]⁻, but smaller than that in the protonated water dimer. The different bonding structures substantially affect the barrier to proton transfer, even though they are isoelectronic systems. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 357–367, 1999     

35Cl NQR studies of 1‐chloro‐2,4‐dinitrobenzene and 1,2‐dichloro‐3‐nitrobenzene as a function of pressure and temperature

The temperature and pressure dependences of ³⁵Cl nuclear quadrupole resonance (NQR) frequency and spin–lattice relaxation time (T₁) were investigated for 1‐chloro‐2,4‐dinitrobenzene and 1,2‐dichloro‐3‐nitrobenzene. T₁ was measured in the temperature range 77–300 K. Furthermore, the NQR frequency (ν) and T₁ for these compounds were measured as a function of pressure up to 5.1 kbar at 300 K. Relaxation was found to be due to the torsional motion of the molecule and the reorientation motion of the nitro group. By analysing the temperature dependence of T₁, the activation energy for the reorientation motion of the nitro group was obtained. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities W₁ and W₂ for the Δm = ±1 and Δm = ±2 transitions, were also obtained. Both compounds showed a non‐linear variation of NQR frequency with pressure. The pressure coefficients were observed to be positive. A thermodynamic analysis of the data was carried out to determine the constant‐volume temperature coefficients of the NQR frequency. The spin–lattice relaxation time T₁ for both the compounds was found to be weakly dependent on pressure, showing that the relaxation is mainly due to the torsional motions. Copyright © 2002 John Wiley & Sons, Ltd.     

35Cl NQR frequency and spin lattice relaxation time in 3,4‐dichlorophenol as a function of pressure and temperature

The pressure dependences of ³⁵Cl nuclear quadrupole resonance (NQR) frequency, temperature and pressure variation of spin lattice relaxation time (T₁) were investigated in 3,4‐dichlorophenol. T₁ was measured in the temperature range 77–300 K. Furthermore, the NQR frequency and T₁ for these compounds were measured as a function of pressure up to 5 kbar at 300 K. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities W₁ and W₂ for the Δm = ±1 and Δm = ±2 transitions were also obtained. A nonlinear variation of NQR frequency with pressure has been observed and the pressure coefficients were observed to be positive. A thermodynamic analysis of the data was carried out to determine the constant volume temperature coefficients of the NQR frequency. An attempt is made to compare the torsional frequencies evaluated from NQR data with those obtained by IR spectra. On selecting the appropriate mode from IR spectra, a good agreement with torsional frequency obtained from NQR data is observed. The previously mentioned approach is a good illustration of the supplementary nature of the data from IR studies, in relation to NQR studies of compounds in solid state. Copyright © 2012 John Wiley & Sons, Ltd.     

Temperature‐ and pressure‐dependent study of 35Cl NQR frequency and spin lattice relaxation time in 2,3‐dichloroanisole

The temperature and pressure dependence of ³⁵Cl NQR frequency and spin lattice relaxation time (T₁) were investigated in 2,3‐dichloroanisole. Two NQR signals were observed throughout the temperature and pressure range studied. T₁ were measured in the temperature range from 77 to 300 K and from atmospheric pressure to 5 kbar. Relaxation was found to be due to the torsional motion of the molecule and also reorientation of motion of the CH₃ group. T₁ versus temperature data were analyzed on the basis of Woessner and Gutowsky model, and the activation energy for the reorientation of the CH₃ group was estimated. The temperature dependence of the average torsional lifetimes of the molecules and the transition probabilities were also obtained. NQR frequency shows a nonlinear behavior with pressure, indicating both dynamic and static effects of pressure. The pressure coefficients were observed to be positive for both the lines. A thermodynamic analysis of the data was carried out to determine the constant volume temperature coefficients of the NQR frequency. The variation of spin lattice time with pressure was very small, showing that the relaxation is mainly due to the torsional motions of the molecules. Copyright © 2010 John Wiley & Sons, Ltd.     

Assessment of substituent effects on the parameters of 35Cl nuclear quadrupole resonance in para‐substituted benzene‐sulphenyl chloride via quantum chemical calculations

In this research, substituent effects on the parameters of ³⁵Cl nuclear quadrupole resonance (NQR) in para‐substituted benzene‐sulphenyl chloride were studied at M062X/6‐311G(d,p) theory level. The ³⁵Cl NQR parameters of the quadrupole coupling constant (QCC) and electric‐field gradient (EFG) tensor, as well as an asymmetric parameter, were shown to be correlated with Hammett constant following their calculations. The frontier orbital energy levels, HOMO‐LUMO gaps, hardness, electrophilicity, and chemical potential values of these molecules were calculated as well. natural bond orbital (NBO) analysis was applied for calculating natural populations at chlorine atoms.     

Computational studies on electron and proton transfer in phenol‐imidazole‐base triads

The electron and proton transfer in phenol‐imidazole‐base systems (base = NH₂^? or OH^?) were investigated by density‐functional theory calculations. In particular, the role of bridge imidazole on the electron and proton transfer was discussed in comparison with the phenol‐base systems (base = imidazole, H₂O, NH₃, OH^?, and NH₂^?). In the gas phase phenol‐imidazole‐base system, the hydrogen bonding between the phenol and the imidazole is classified as short strong hydrogen bonding, whereas that between the imidazole and the base is a conventional hydrogen bonding. The n value in spⁿ hybridization of the oxygen and carbon atoms of the phenolic CO sigma bond was found to be closely related to the CO bond length. From the potential energy surfaces without and with zero point energy correction, it can be concluded that the separated electron and proton transfer mechanism is suitable for the gas‐phase phenol‐imidazole‐base triads, in which the low‐barrier hydrogen bond is found and the delocalized phenolic proton can move freely in the single‐well potential. For the gas‐phase oxidized systems and all of the triads in water solvent, the homogeneous proton‐coupled electron transfer mechanism prevails. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Spectroscopic,thermal studies and molecular modelling of charge transfer complexation between 5-amino-2-methoxypyridine with chloranilic acid in different polar solvents

Charge transfer (CT) interaction between 5-amino-2-methoxypyridine (5AMPy), as electron donor (proton acceptor), with 3,6-dichloro-2,5-dihydroxy-p-benzoquinone (chloranilic acid, H₂CA), as electron acceptor (proton donor), has been investigated spectrophotometrically in the polar protic solvents ethanol (EtOH) and methanol (MeOH) and the aprotic one acetonitrile (AN). Pink-coloured solution is formed instantaneously upon mixing 5AMPy with H₂CA solutions in all solvents, which is the hallmark evidence of CT complex formation. Based on Job’s method of continuous variations, as well as spectrophotometric titrations, the stoichiometry of the complex was found to be 1:1 [(5AMPy) (H₂CA)] in all solvents. Benesi–Hildebrand equation has been applied to estimate the formation constant of the produced CT complex (K_CT) and its molar absorptivity (ε), they reached high values, confirming the complex high stability. Solid CT complex has been synthesised and analysed by elemental analyses and FTIR, ¹H NMR spectroscopies, where 2:1 [(5AMPy)₂ (H₂CA)] CT complex was obtained.     

Conformations and intermolecular interactions pattern in solid chloroxylenol and triclosan (API of anti‐infective agents and drugs). A 35Cl NQR, 1H‐14 N NQDR,X‐ray and DFT/QTAIM study

Two antibacterial and antifungal agents, chloroxylenol (4‐chloro‐3,5‐dimethyl‐phenol) and triclosan (5‐chloro‐2‐(2’,4’‐dichlorophenoxy)‐phenol), were studied experimentally in solid state with an X‐ray, ³⁵Cl‐nuclear quadrupole resonance (NQR) and ¹⁷O‐nuclear quadrupole double resonance (NQDR) spectroscopies and, theoretically, with the density functional theory/quantum theory of atoms in molecules (DFT/QTAIM). The crystallographic structure of triclosan, which crystallises in space group P3₁ with one molecule in the asymmetric unit [a = 12.64100(10), b = 12.64100(10), c = 6.71630(10) Å], was solved with an X‐ray and refined to a final R‐factor of 2.81% at room temperature. The NQR frequencies of ³⁵Cl and ¹⁷O were detected with the help of the density functional theory (DFT) assigned to particular chlorine and oxygen sites in the molecules of both compounds. The NQR frequencies at ³⁵Cl sites in chloroxylenol and triclosan were found to be more differentiated than frequencies at the ¹⁷O site. The former better describes the substituent withdrawing effects connected to π‐electron delocalization within the benzene rings and the influence of temperature; whereas, those at the ¹⁷O site provide more information on O‐H bond and intermolecular interactions pattern. The conformation adopted by diphenyl ether of triclosan in solid state was found to be typical of diphenyl ethers, but the opposite to those adopted when it was bound to different inhibitors. According to an X‐ray study, temperature had no effect on the conformation of the diphenyl ring of triclosan, which was the same at 90 K and at room temperature (RT). The scattering of NQR frequencies reproduced by the DFT under assumption of the X‐ray data at 90 K and RT is found to be a good indicator of the quality of resolution of the crystallographic structure. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrogen‐bonded assemblies in the molecular crystals of 2,2′‐thiodiacetic acid with ethylenediamine and o‐phenylenediamine

Carboxylate molecular crystals have been of interest due to the presence of hydrogen bonding, which plays a significant role in chemical and crystal engineering, as well as in supramolecular chemistry. Acid–base adducts possess hydrogen bonds which increase the thermal and mechanical stability of the crystal. 2,2′‐Thiodiacetic acid (Tda) is a versatile ligand that has been widely explored, employing its multidendate and chelating coordination abilities with many metals; however, charge‐transfer complexes of thiodiacetic acid have not been reported. Two salts, namely ethylenediaminium 2,2′‐thiodiacetate, C₂H₁₀N₂²⁺·C₄H₄O₄S₂²⁻, denoted Tdaen, and 2‐aminoanilinium 2‐(carboxymethylsulfanyl)acetate, C₆H₉N₂⁺·C₄H₅O₄S⁻, denoted Tdaophen, were synthesized and characterized by IR, ¹H and ¹³C NMR spectroscopies, and single‐crystal X‐ray diffraction. In these salts, Tda reacts with the aliphatic (ethylenediamine) and aromatic (o‐phenylenediamine) diamines, and deprotonates them to form anions with different valencies and different supramolecular networks. In Tdaen, the divalent Tda²⁻ anions form one‐dimensional linear supramolecular chains and these are extended into a three‐dimensional sandwich‐type supramolecular network by interaction with the ethylenediaminium cations. However, in Tdaophen, the monovalent Tda⁻ anions form one‐dimensional zigzag supramolecular chains, which are extended into a three‐dimensional supramolecular network by interaction with the 2‐aminoanilinium cations. Thus, both three‐dimensional structures display different ring motifs. The structures of these diamines, which are influenced by hydrogen‐bonded assemblies in the molecular crystals, are discussed in detail.     

Competitive proton and hydride transfer reactions via ion‐neutral complexes: fragmentation of deprotonated benzyl N‐phenylcarbamates in mass spectrometry

The gas‐phase chemistry of deprotonated benzyl N‐phenylcarbamates was investigated by electrospray ionization tandem mass spectrometry. Characteristic losses of a substituted phenylcarbinol and a benzaldehyde from the precursor ion were proposed to be derived from an ion‐neutral complex (INC)‐mediated competitive proton and hydride transfer reactions. The intermediacy of the INC consisting of a substituted benzyloxy anion and a phenyl isocyanate was supported by both ortho‐site‐blocking experiments and density functional theory calculations. Within the INC, the benzyloxy anion played the role of either a proton abstractor or a hydride donor toward its neutral counterpart. Relative abundances of the product ions were influenced by the nature of the substituents. Electron‐withdrawing groups at the N‐phenyl ring favored the hydrogen transfer process (including proton and hydride transfer), whereas electron‐donating groups favored direct decomposition to generate the benzyloxy anion (or substituted benzyloxy anion). By contrast, electron‐withdrawing and electron‐donating substitutions at the O‐benzyl ring exhibited opposite effects. Copyright © 2015 John Wiley & Sons, Ltd.     

Different molecular conformations co‐exist in each of three 2‐aryl‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamides: hydrogen bonding in zero,one and two dimensions

4‐Antipyrine [4‐amino‐1,5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one] and its derivatives exhibit a range of biological activities, including analgesic, antibacterial and anti‐inflammatory, and new examples are always of potential interest and value. 2‐(4‐Chlorophenyl)‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamide, C₁₉H₁₈ClN₃O₂, (I), crystallizes with Z′ = 2 in the space group P, whereas its positional isomer 2‐(2‐chlorophenyl)‐N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)acetamide, (II), crystallizes with Z′ = 1 in the space group C2/c; the molecules of (II) are disordered over two sets of atomic sites having occupancies of 0.6020 (18) and 0.3980 (18). The two independent molecules of (I) adopt different molecular conformations, as do the two disorder components in (II), where the 2‐chlorophenyl substituents adopt different orientations. The molecules of (I) are linked by a combination of N—H…O and C—H…O hydrogen bonds to form centrosymmetric four‐molecule aggregates, while those of (II) are linked by the same types of hydrogen bonds forming sheets. The related compound N‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)‐2‐(3‐methoxyphenyl)acetamide, C₂₀H₂₁N₃O₃, (III), is isomorphous with (I) but not strictly isostructural; again the two independent molecules adopt different molecular conformations, and the molecules are linked by N—H…O and C—H…O hydrogen bonds to form ribbons. Comparisons are made with some related structures, indicating that a hydrogen‐bonded R₂²(10) ring is the common structural motif.     

Structures of CoII and ZnII complexes of the proton‐transfer compound derived from pyrazine‐2,3‐dicarboxylic acid and piperazine

The reaction of the proton‐transfer compound piperazine‐1,4‐diium pyrazine‐2,3‐dicarboxylate 4.5‐hydrate, C₄H₁₂N₂²⁺·C₆H₂N₂O₄²⁻·4.5H₂O or (pipzH₂)(pyzdc)·4.5H₂O (pyzdcH₂ is pyrazine‐2,3‐dicarboxylic acid and pipz is piperazine), (I), with Zn(NO₃)₂·6H₂O and CoCl₂·6H₂O results in the formation of bis(piperazine‐1,4‐diium) bis(μ‐pyrazine‐2,3‐dicarboxylato)‐κ³N¹,O²:O³;κ³O³:N¹,O²‐bis[aqua(pyrazine‐2,3‐dicarboxylato‐κ²N¹,O²)zinc(II)] decahydrate, (C₄H₁₂N₂)₂[Zn₂(C₆H₂N₂O₄)₄(H₂O)₂]·10H₂O or (pipzH₂)₂[Zn(pyzdc)₂(H₂O)]₂·10H₂O, (II), and catena‐poly[piperazine‐1,4‐diium [cobalt(II)‐bis(μ‐pyrazine‐2,3‐dicarboxylato)‐κ³N¹,O²:O³;κ³O³:N¹,O²] hexahydrate], {(C₄H₁₂N₂)[Co(C₆H₂N₂O₄)₂]·6H₂O}_n or {(pipzH₂)[Co(pyzdc)₂]·6H₂O}_n, (III), respectively. In (I), pyzdcH₂ is doubly deprotonated on reaction with piperazine as a base. Compound (II) crystallizes as a dimer, whereas compound (III) exists as a one‐dimensional coordination polymer. In (II), two pyzdc²⁻ groups chelate to each of the two Zn^II atoms through a ring N atom and an O atom of the 2‐carboxylate group. In one ligand, the adjacent 3‐carboxylate group bridges to a neighbouring metal atom. A water molecule ligates in the sixth coordination site. The structure of (II) can be described as a commensurate superlattice due to an ordering in the hydrogen‐bonded network. In (III), no water is coordinated to the metal atom and the coordination sphere is comprised of two N,O‐chelates plus two bridging O atoms. A large number of hydrogen bonds are observed in all three compounds. These interactions, as well as π–π and C=O...π stacking interactions, play important structural roles.     

Complexes of Eu(III), Tb(III) and Cu(II) with proton transfer compound between 2,6-pyridinedicarboxylic acid and 2-aminobenzothiazole: characterization of the structures and physical properties

A proton transfer compound, (ABTH)⁺(PydcH)^? (1), obtained from 2-aminobenzothiazole (ABT) and 2,6-pyridinedicarboxylic acid (Pydc) as well as its Eu(III), Tb(III), and Cu(II) complexes (ABT)₃[Eu(Pydc)₃]·5H₂O (2), (ABT)₃[Tb(Pydc)₃]·5H₂O (3), and (ABT)[Cu(Pydc)(PydcH)]·3H₂O (4) were obtained under ambient conditions and structurally verified by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA), and magnetic measurements. Compounds 2–4 are the first known solids containing complex anions with Pydc ligands, 2-aminobenzothiazole cations (ABT), and solvate water molecules. During the synthesis of 3, a secondary phase with the formula ABTCl?H₂O was obtained and characterized by elemental analysis and single-crystal X-ray diffraction. The asymmetric unit of 5 consists of six symmetry independent ABT cations, six chlorides, and six water molecules. The two lanthanide complexes showed characteristic emissions of Eu³⁺ and Tb³⁺ ions. The good solubilities of these complexes in water and their luminescence properties make them attractive luminescent labels of biological molecules.     

Dual roles of alkyl alcohols as syndiotactic‐specificity inducers and accelerators in the radical polymerization of N‐isopropylacrylamide and some properties of syndiotactic poly(N‐isopropylacrylamide)

The effects of simple alkyl alcohols on the radical polymerization of N‐isopropylacrylamide in toluene at low temperatures were investigated. We succeeded in the induction of syndiotactic specificity and the acceleration of polymerization reactions at the same time by adding simple alkyl alcohols such as 3‐methyl‐3‐pentanol (3Me3PenOH) to N‐isopropylacrylamide polymerizations. The dyad syndiotacticity increased with a decrease in the temperature and an increase in the bulkiness of the added alcohol and reached up to 71% at ?60 °C in the presence of 3Me3PenOH. With the assistance of NMR analysis, it was revealed that the alcohol compounds played dual roles in this polymerization system; an alcohol compound coordinating to the N? H proton induced syndiotactic specificity, and that hydrogen‐bonded to the C?O oxygen accelerated the polymerization reaction. The effect of syndiotacticity on the properties of poly(N‐isopropylacrylamide)s was also examined in some detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4450–4460, 2006