Cavity ring‐down study of BrO radicals: Kinetics of the Br + O3 reaction and rate of relaxation of vibrationally excited BrO by collisions with N2 and O2

Cavity ring‐down (CRD) techniques were used to study the kinetics of the reaction of Br atoms with ozone in 1–205 Torr of either N₂ or O₂, diluent at 298 K. By monitoring the rate of formation of BrO radicals, a value of k(Br + O₃) = (1.2 ± 0.1) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ was established that was independent of the nature and pressure of diluent gas. The rate of relaxation of vibrationally excited BrO radicals by collisions with N₂ and O₂ was measured; k(BrO(v) + O₂ → BrO(v − 1) + O₂) = (5.7 ± 0.3) × 10⁻¹³ and k(BrO(v) + N₂ → BrO(v − 1) + N₂) = (1.5 ± 0.2) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹. The increased efficiency of O₂ compared with N₂ as a relaxing agent for vibrationally excited BrO radicals is ascribed to the formation of a transient BrO–O₂ complex. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 125–130, 2000     

Indole- and carbazole-substituted pyridinium iodide salts: a rare case of conformational isomerism in crystals

A series of indole- and carbazole-substituted pyridinium iodide salts has been synthesized and characterized. X-ray analysis revealed that the iodide salt of the indole-substituted cation (E)-4-(1H-indol-3-yl­vinyl)-N-methyl­pyridinium (IMPE⁺), C₁₆H₁₅N₂⁺·I⁻, (I), has two polymorphic modifications, (Ia) and (Ib), and a hemihydrate structure, C₁₆H₁₅N₂⁺·I⁻·0.5H₂O, (II). Until now, only one crystal modi­fication has been identified for the (E)-4-(9-ethyl-9H-carbazol-3-yl­vinyl)-N-methyl­pyridinium (ECMPE⁺) iodide salt, C₂₂H₂₁N₂⁺·I⁻, (III). Crystals of (Ia) and (Ib) comprise stacks of antiparallel cations with iodide anions located in the channels between the stacks. Due to the presence of the water mol­ecules, the packing in (II) is quite different to that found in (Ia) and (Ib), and positional disorder involving a statistical superposition of two rotamers of IMPE⁺, with different orientations of the indole fragment, was found. Crystals of (III) contain two independent ECMPE⁺ rotamers with different orientations of their carbazole substituents. The cations are packed in stacks, with the iodide anions located in the channels between the stacks. In (III), the iodide was found to be disordered over two sites, with occupancies of 0.83 and 0.17.     

The hydrochloride and hydrobromide salt forms of (S)‐amphetamine

Despite the high profile of amphetamine, there have been relatively few structural studies of its salt forms. The lack of any halide salt forms is surprising as the typical synthetic route for amphetamine initially produces the chloride salt. (S)‐Amphetamine hydrochloride [systematic name: (2S)‐1‐phenylpropan‐2‐aminium chloride], C₉H₁₄N⁺·Cl⁻, has a Z′ = 6 structure with six independent cation–anion pairs. That these are indeed crystallographically independent is supported by different packing orientations of the cations and by the observation of a wide range of cation conformations generated by rotation about the phenyl–CH₂ bond. The supramolecular contacts about the anions also differ, such that both a wide variation in the geometry of the three N—H...Cl hydrogen bonds formed by each chloride anion and differences in C—H...Cl contacts are apparent. (S)‐Amphetamine hydrobromide [systematic name: (2S)‐1‐phenylpropan‐2‐aminium bromide], C₉H₁₄N⁺·Br⁻, is broadly similar to the hydrochloride in terms of cation conformation, the existence of three N—H...X hydrogen‐bond contacts per anion and the overall two‐dimensional hydrogen‐bonded sheet motif. However, only the chloride structure features organic bilayers and Z′ > 1.     

Living cationic polymerization of vinyl ethers and styrene derivatives: Design of initiating systems based on added salts with halogen anions

This paper overviews three living cationic polymerization systems (for styrene, p-methoxystyrene, and isobutyl vinyl ether) that are, in common, featured by: (i) specifically in nonpolar solvents, the use of the hydrogen halide/metal halide initiating systems (HX/MX_n; X: I, Br, Cl; MX_n: ZnX₂, SnCl₄), which generate a living growing carbocation stabilized by a nucleophilic counteranion (X⁻…MX_n); (ii) specifically in polar solvents, the use of externally added ammonium salts (nBu₄N⁺Y⁻; Y⁻: I⁻, Br⁻, Cl⁻), which permit the generation of living species from HX/MX_n by providing nucleophilic halogen anions Y⁻, either the same as or different from the halogen X⁻ in HX.     

Single-ion and salt conductor polymer electrolytes based on poly(4-vinylpyridine) quaternized with poly(ethylene oxide) side chains

A new type of single-ion conductor with fixed cation was synthesized by spontaneous anionic polymerization of 4-vinylpyridine in the presence of short polyethylene oxide ( PEO ) chains as alkylating agents. These comblike polymers have low T_gs and are amorphous with the shorter PEO s. Their conductivities are unaffected by the nature of the anion ( Br ⁻, ClO ₄⁻, and tosylate) and are controlled by the free volume and the mobility of the pendant cation. By comparison of the results at constant free volume, it is shown that the charge density decreases with the increasing length of pendant PEO demonstrating that PEO acts only as a plasticizing agent. Best conductivity results (σ = 10⁻⁵ S cm⁻¹ at 60°C) are obtained with PEO side chains of molecular weight 350. With this sample, the conductivity in the presence of various amounts of added salt (LiTFSI) was studied. A best value of 10⁻⁴ S cm⁻¹ at 60°C is obtained with a molar ratio EO/Li of 10. It is shown that, over the range of examined concentrations (0.2–1.3 mol Li kg⁻¹), the reduced conductivity σ_r/c increases linearly with increasing salt concentration showing that the ion mobility increases continuously. Such behavior is quite unusual since in this concentration range a maximum is generally observed with PEO systems. To interpret this result and by analogy with the behavior of this type of polymer in solution, it is proposed that the conformation of these polymers in the solid state is segregated with the P4VP skeleton more or less confined inside the dense coils surrounded by the PEO side chains. Under the influence of the increasing salt concentration, this microphase separation vanishes progressively: The LiTFSI salt exchanges with the tosylate anions and acts as a miscibility improver agent. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2719–2728, 1997     

Structural study of six cycloalkylammonium cinnamate salt structures featuring one‐dimensional columns and two‐dimensional hydrogen‐bonded networks

Six ammonium carboxylate salts, namely cyclopentylammonium cinnamate, C₅H₁₂N⁺·C₉H₇O₂⁻, (I), cyclohexylammonium cinnamate, C₆H₁₄N⁺·C₉H₇O₂⁻, (II), cycloheptylammonium cinnamate form I, C₇H₁₆N⁺·C₉H₇O₂⁻, (IIIa), and form II, (IIIb), cyclooctylammonium cinnamate, C₈H₁₈N⁺·C₉H₇O₂⁻, (IV), and cyclododecylammonium cinnamate, C₁₂H₂₆N⁺·C₉H₇O₂⁻, (V), are reported. Salts (II)–(V) all have a 1:1 ratio of cation to anion and feature three N⁺—H...O⁻ hydrogen bonds forming one‐dimensional hydrogen‐bonded columns consisting of repeating R₄³(10) rings, while salt (I) has a two‐dimensional network made up of alternating R₄⁴(12) and R⁶₈(20) rings. Salt (III) consists of two polymorphic forms, viz. form I having Z′ = 1 and form II with Z′ = 2. The latter polymorph has disorder of the cycloheptane rings in the two cations, as well as whole‐molecule disorder of one of the cinnamate anions. A similar, but ordered, Z′ = 2 structure is seen in salt (IV).     

A dihydrogen phosphate anionic network as a host lattice for cations in 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate) and 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1)

In the salt 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate), C₅H₁₃N₂²⁺·2H₂PO₄⁻, (I), and the solvated salt 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1), C₁₀H₉N₂⁺·H₂PO₄⁻·H₃PO₄, (II), the formation of O—H...O and N—H...O hydrogen bonds between the dihydrogen phosphate (H₂PO₄⁻) anions and the cations constructs a three‐ and two‐dimensional anionic–cationic network, respectively. In (I), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional pseudo‐honeycomb‐like supramolecular architecture along the (010) plane. 1‐Methylpiperazine‐1,4‐diium cations are trapped between the (010) anionic layers through three N—H...O hydrogen bonds. In solvated salt (II), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional supramolecular architecture with open channels projecting along the [001] direction. The 2‐(pyridin‐2‐yl)pyridinium cations are trapped between the open channels by N—H...O and C—H...O hydrogen bonds. From a study of previously reported structures, dihydrogen phosphate anions show a supramolecular flexibility depending on the nature of the cations. The dihydrogen phosphate anion may be suitable for the design of the host lattice for host–guest supramolecular systems.     

Polar hydrogen‐bonded organic chains in 4,4′‐bipyrazolium bromide and perchlorate monohydrates

4,4′‐Bipyrazolium [or 4‐(1H‐pyrazol‐4‐yl)pyrazolium] bromide monohydrate, C₆H₇N₄⁺·Br⁻·H₂O, and 4,4′‐bipyrazolium perchlorate monohydrate, C₆H₇N₄⁺·ClO₄⁻·H₂O, have closely related layered structures involving tight stacks of antiparallel N—H⋯N hydrogen‐bonded polar bipyrazolium chains [N⋯N = 2.712 (3) and 2.742 (2) Å], which are crosslinked by hydrogen bonds with water mol­ecules and counter‐anions.     

The nature of the growing species in living cationic polymerization: Principles,stereochemistry, and in-situ NMR analysis

The objective of this paper is to discuss: (i) the general approaches to living cationic polymerizations; (ii) the nature of the growing species thus generated. For the first, it is concluded that three general methods are currently available which involve the nucleophilic stabilization of the growing carbocations by (a) a suitable counteranion, (b) an added Lewis base, or (c) an added neutral salt. According to this view, a variety of initiating systems are classified. For the second, findings are presented for the recently developed living cationic polymerization of vinyl ethers by the HCl/SnCl₄ initiating system in the presence of an added salt (nBu₄N⁺Cl⁻). The nature of the growing species therein is discussed on the basis of the steric structure of the living polymers, relative to nonliving counterparts, and the in-situ ¹³C NMR spectroscopic analysis of model reactions where the interaction of the growing end model [CH₃CH(OR)Cl] with SnCl₄ and the added salt is analyzed.     

Spectral,kinetics, and redox properties of the transients formed on one‐electron oxidation of 4,4′‐thiodiphenol: A pulse radiolysis study

The transient absorption bands (λ_max = 330, 525 nm, k_f = 5 × 10⁹ dm³ mol⁻¹ s⁻¹) obtained on pulse radiolysis of N₂O‐saturated neutral aqueous solution of 4,4′‐thiodiphenol (TDPH) are due to the reaction of TDPH with ^·OH radicals and are assigned to phenoxyl radical formed on fast deprotonation of the solute radical cation. The reaction of specific one‐electron oxidants (Cl₂^·−, Br₂^·−, N₃^·, TI²⁺, CCl₃OO^·) with TDPH also produced similar transient absorption bands. The phenoxyl radicals are also produced on pulse radiolysis of N₂‐saturated solution of TDPH in 1,2‐dichloroethane. The nature of transient absorption spectrum obtained on reaction of ^·OH radicals with TDPH is not affected in acidic solutions, showing that OH‐adduct is not formed in neutral solutions. The oxidation potential for the formation of phenoxyl radical is determined to be 0.98 V. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 603–610, 1999     

Temperature-induced formation of two dinuclear dysprosium complexes with different magnetic properties

A dinuclear Dy (III) complex [Dy₂( L ¹ )₂(NO₃)₄]·2CH₃CN ( 1 ) (H L ¹ = 1,3-bis{[(E)-pyridin-2-ylmethylene]amino}propan-2-ol) was obtained via the reaction of 1,3-diamino-2-propanol, 2-pyridyaldehyde and Dy (NO₃)₃·6H₂O at room temperature. In the structure of complex 1 , two Dy (III) ions are in the N₄O₆ coordination environment provided by NO₃⁻ and ( L ¹ )⁻, and both of these ions are in the sphenocorona configuration. [Dy₂( L ² )₂(NO₃)₄] ( 2 ) [H L ² = 2-(pyridin-2-yl)hexahydropyrimidin-5-ol] was obtained using the same reaction material only when the reaction temperature was changed to 60°C. Structural analysis of complex 2 showed that the two Dy (III) ions with the same coordination configuration are in the N₃O₆ coordination environment provided by NO₃⁻ and ( L ² )⁻ and are in the distorted spherical-capped square antiprism. Surprisingly, H L ² with the parent of bipyridine was synthesized by the Schiff base reaction of 1,3-diamino-2-propanol with 2-pyridoxaldehyde followed by the ring-closing reaction catalyzed by Dy (III) ions. Magnetic measurements of the Dy (III) complexes revealed no obvious frequency-dependent behavior of complex 1 . In contrast, complex 2 showed an obvious frequency dependence (U_eff = 0.49 K and τ₀ = 6.62 × 10⁻⁴ s) under the condition of zero field and a weak double relaxation behavior (U_eff = 9.25 K and τ₀ = 9.70 × 10⁻⁴ s) at 1500 Oe.     

Stereoselective Copolymerization of Unprotected Polar and Nonpolar Styrenes by an Yttrium Precursor: Control of Polar‐Group Distribution and Mechanism

Styrene underwent unprecedented coordination–insertion copolymerization with naked polar monomers (ortho ‐/meta ‐/para ‐methoxystyrene) in the presence of a pyridyl methylene fluorenyl yttrium catalyst. High activity (1.26×10⁶ g mol_Y⁻¹ h⁻¹) and excellent syndioselectivity were observed, and high‐molecular‐weight copolymers (24.6×10⁴ g mol⁻¹) were obtained. The insertion rate of the polar monomers could be adjusted in the full range of 0–100 % simply by changing the loading of the polar styrene monomer. Strikingly, the copolymers had tapered, gradient, and even random sequence distributions, depending on the position of the polar methoxy group on the phenyl ring and thus on its mode of coordination to the active metal center, as shown by tracking the polymerization process and DFT calculations.     

High-level computational study on the thermochemistry of saturated and unsaturated three- and four-membered nitrogen and phosphorus rings

The heats of formation and strain energies for saturated and unsaturated three- and four-membered nitrogen and phosphorus rings have been calculated using G2 theory. G2 heats of formation (ΔH_f298) of triaziridine [(NH)₃], triazirine (N₃H), tetrazetidine [(NH)₄], and tetrazetine (N₄H₂) are 405.0, 453.7, 522.5, and 514.1 kJ mol⁻¹, respectively. Tetrazetidine is unstable (121.5 kJ mol⁻¹ at 298 K) with respect to its dissociation into two trans-diazene (N₂H₂) molecules. The dissociation of tetrazetine into molecular nitrogen and trans-diazene is highly exothermic (ΔH₂₉₈ = −308.3 kJ mol⁻¹ calculated using G2 theory). G2 heats of formation (ΔH_f298) of cyclotriphosphane [(PH)₃], cyclotriphosphene (P₃H), cyclotetraphosphane [(PH)₄], and cyclotetraphosphene (P₄H₂) are 80.7, 167.2, 102.7, and 170.7 kJ mol⁻¹, respectively. Cyclotetraphosphane and cyclotetraphosphene are stabilized by 145.8 and 101.2 kJ mol⁻¹ relative to their dissociations into two diphosphene molecules or into diphosphene (HP(DOUBLE BOND)PH) and diphosphorus (P₂), respectively. The strain energies of triaziridine [(NH)₃], triazirine (N₃H), tetrazetidine [(NH)₄], and tetrazetine (N₄H₂) were calculated to be 115.0, 198.3, 135.8, and 162.0 kJ mol⁻¹, respectively (at 298 K). While the strain energies of the nitrogen three-membered rings in triaziridine and triazirine are smaller than the strain energies of cyclopropane (117.4 kJ mol⁻¹) and cyclopropene (232.2 kJ mol⁻¹), the strain energies of the nitrogen four-membered rings in tetrazetidine and tetrazetine are larger than those of cyclobutane (110.2 kJ mol⁻¹) and cyclobutene (132.0 kJ mol⁻¹). In contrast to higher strain in cyclopropane as compared with cyclobutane, triaziridine is less strained than tetrazetidine. The strain energies of cyclotriphosphane [(PH)₃, 21.8 kJ mol⁻¹], cyclotriphosphene (P₃H, 34.6 kJ mol⁻¹), cyclotetraphosphane [(PH)₄, 24.1 kJ mol⁻¹], and cyclotetraphosphene (P₄H₂, 18.5 kJ mol⁻¹), calculated at the G2 level are considerably smaller than those of their carbon and nitrogen analog. Cyclotetraphosphene containing the P(DOUBLE BOND)P double bond is less strained than cyclotetraphosphane, in sharp contrast to the ratio between the strain energies for the analogous unsaturated and saturated carbon and nitrogen rings. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62 : 373–384, 1997     

Enhanced third‐order nonlinear optical properties determined in thin films using the Z‐scan technique: bis(μ‐4,4′‐oxydibenzoato)bis[(4′‐phenyl‐2,2′:6′,2′′‐terpyridine)cobalt(II)]

π‐Conjugated organic materials exhibit high and tunable nonlinear optical (NLO) properties, and fast response times. 4′‐Phenyl‐2,2′:6′,2′′‐terpyridine (PTP) is an important N‐heterocyclic ligand involving π‐conjugated systems, however, studies concerning the third‐order NLO properties of terpyridine transition metal complexes are limited. The title binuclear terpyridine Co^II complex, bis(μ‐4,4′‐oxydibenzoato)‐κ³O,O′:O′′;κ³O′′:O,O′‐bis[(4′‐phenyl‐2,2′:6′,2′′‐terpyridine‐κ³N,N′,N′′)cobalt(II)], [Co₂(C₁₄H₈O₅)₂(C₂₁H₁₅N₃)₂], (1), has been synthesized under hydrothermal conditions. In the crystal structure, each Co^II cation is surrounded by three N atoms of a PTP ligand and three O atoms, two from a bidentate and one from a symmetry‐related monodentate 4,4′‐oxydibenzoate (ODA²⁻) ligand, completing a distorted octahedral coordination geometry. Neighbouring [Co(PTP)]²⁺ units are bridged by ODA²⁻ ligands to form a ring‐like structure. The third‐order nonlinear optical (NLO) properties of (1) and PTP were determined in thin films using the Z‐scan technique. The title compound shows a strong third‐order NLO saturable absorption (SA), while PTP exhibits a third‐order NLO reverse saturable absorption (RSA). The absorptive coefficient β of (1) is −37.3 × 10⁻⁷ m W⁻¹, which is larger than that (8.96 × 10⁻⁷ m W⁻¹) of PTP. The third‐order NLO susceptibility χ⁽³⁾ values are calculated as 6.01 × 10⁻⁸ e.s.u. for (1) and 1.44 × 10⁻⁸ e.s.u. for PTP.     

Cavity ring‐down spectroscopic study of the kinetics of the reactions of FCO radicals with O2 and NO at 295 K

Cavity ring‐down UV absorption spectroscopy was used to study the kinetics of the recombination reaction of FCO radicals and the reactions with O₂ and NO in 4.0–15.5 Torr total pressure of N₂ diluent at 295 K. k(FCO + FCO) is (1.8 ± 0.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The pressure dependence of the reactions with O₂ and NO in air at 295 K is described using a broadening factor of Fc = 0.6 and the following low (k₀) and high (k_∞) pressure limit rate constants: k₀(FCO + O₂) = (8.6 ± 0.4) × 10⁻³¹ cm⁶ molecule⁻¹ s⁻¹, k_∞(FCO + O₂) = (1.2 ± 0.2) × 10⁻¹² cm³ molecule⁻¹ s⁻¹, k₀(FCO + NO) = (2.4 ± 0.2) × 10⁻³⁰ cm⁶ molecule⁻¹ s⁻¹, and k_∞ (FCO + NO) = (1.0 ± 0.2) × 10⁻¹² cm³ molecule⁻¹ s⁻¹. The uncertainties are two standard deviations. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 130–135, 2001     

A novel thio­cyanate‐bridged one‐dimensional chain complex: [Cu(NCS)2(Hambi)] (Hambi is 2‐amino­methyl‐1H‐benz­imidazole)

Using 2‐amino­methyl‐1H‐benz­imidazole as the ligand, a new thio­cyanate‐bridged copper(II) complex, namely bis(2‐aminomethyl‐1H‐benz­imidazole‐κ²N²,N³)­di­thio­cyanato­copper(II),[Cu(NCS)₂(C₈H₉N₃)], has been synthesized and structurally characterized. The Cu atom is five‐coordinated and exhibits a distorted square‐pyramidal geometry. The thio­cyanate ions (NCS⁻) act as either bridging or terminal ligands. The bridging NCS⁻ ligands connect neighboring Cu atoms, constructing chains, while the terminal NCS⁻ ligands form hydrogen bonds with amine H atoms, leading to a complicated network.     

A synchrotron radiation study of the one‐dimensional complex of sodium with (1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d‐ribitol,a member of the 'immucillin' family

The sodium salt of [immucillin‐A–CO₂H]⁻ (Imm‐A), namely catena‐poly[[[triaquadisodium(I)](μ‐aqua)[μ‐(1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d ‐ribitol][triaquadisodium(I)][μ‐(1S)‐N‐carboxylato‐1‐(9‐deazaadenin‐9‐yl)‐1,4‐dideoxy‐1,4‐imino‐d ‐ribitol]] tetrahydrate], {[Na₂(C₁₂H₁₃N₄O₆)₂(H₂O)₇]·4H₂O}_n, (I), forms a polymeric chain via Na⁺—O interactions involving the carboxylate and keto O atoms of two independent Imm‐A molecules. Extensive N,O—H...O hydrogen bonding utilizing all water H atoms, including four waters of crystallization, provides crystal packing. The structural definition of this novel compound was made possible through the use of synchrotron radiation utilizing a minute fragment (volume ∼2.4 × 10⁻⁵ mm⁻³) on a beamline optimized for protein data collection. A summary of intra‐ring conformations for immucillin structures indicates considerable flexibility while retaining similar intra‐ring orientations.     

Hirshfeld and DFT analysis of the N‐heterocyclic carbene proligand methylenebis(N‐butylimidazolium) as the acetonitrile‐solvated diiodide salt

N‐Heterocyclic carbene (NHC) based systems are usually exploited in the exploration of catalytic mechanisms and processes in organocatalysis, and homo‐ and heterogeneous catalysis. However, their molecular structures have not received adequate attention. The NHC proligand methylenebis(N‐butylimidazolium) has been synthesized as the acetonitrile solvate of the diiodide salt, C₁₅H₂₆N₄²⁺·2I⁻·CH₃CN [1,1′‐methylenebis(3‐butylimidazolium) diiodide acetonitrile monosolvate], and fully characterized. An interesting cation–anion connection pattern has been identified in the crystal lattice, in which three iodide anions interact simultaneously with the cisoid‐oriented cation. A Hirshfeld surface analysis reveals the predominance of hydrogen bonding over anion–π interactions. This particular arrangement is observed in different methylene‐bridged bis(imidazolium) cations bearing chloride or bromide counter‐anions. Density functional theory (DFT) calculations with acetonitrile as solvent reproduce the geometry of the title cation.     

Salt forms of the pharmaceutical amide dihydrocarbamazepine

Carbamazepine (CBZ) is well known as a model active pharmaceutical ingredient used in the study of polymorphism and the generation and comparison of cocrystal forms. The pharmaceutical amide dihydrocarbamazepine (DCBZ) is a less well known material and is largely of interest here as a structural congener of CBZ. Reaction of DCBZ with strong acids results in protonation of the amide functionality at the O atom and gives the salt forms dihydrocarbamazepine hydrochloride {systematic name: [(10,11‐dihydro‐5H‐dibenzo[b,f]azepin‐5‐yl)(hydroxy)methylidene]azanium chloride, C₁₅H₁₅N₂O⁺·Cl⁻}, dihydrocarbamazepine hydrochloride monohydrate {systematic name: [(10,11‐dihydro‐5H‐dibenzo[b,f]azepin‐5‐yl)(hydroxy)methylidene]azanium chloride monohydrate, C₁₅H₁₅N₂O⁺·Cl⁻·H₂O} and dihydrocarbamazepine hydrobromide monohydrate {systematic name: [(10,11‐dihydro‐5H‐dibenzo[b,f]azepin‐5‐yl)(hydroxy)methylidene]azanium bromide monohydrate, C₁₅H₁₅N₂O⁺·Br⁻·H₂O}. The anhydrous hydrochloride has a structure with two crystallographically independent ion pairs (Z′ = 2), wherein both cations adopt syn conformations, whilst the two hydrated species are mutually isostructural and have cations with anti conformations. Compared to neutral dihydrocarbamazepine structures, protonation of the amide group is shown to cause changes to both the molecular (C=O bond lengthening and C—N bond shortening) and the supramolecular structures. The amide‐to‐amide and dimeric hydrogen‐bonding motifs seen for neutral polymorphs and cocrystalline species are replaced here by one‐dimensional polymeric constructs with no direct amide‐to‐amide bonds. The structures are also compared with, and shown to be closely related to, those of the salt forms of the structurally similar pharmaceutical carbamazepine.     

Hydrogen‐bonding one‐dimensional chains containing the R42(8) motif in the ammonium salts 1‐naphthylammonium iodide and naphthalene‐1,8‐diyldiammonium diiodide

In 1‐naphthylammonium iodide, C₁₀H₁₀N⁺·I⁻, and naphthalene‐1,8‐diyldiammonium diiodide, C₁₀H₁₂N₂²⁺·2I⁻, the predominant hydrogen‐bonding pattern can be described using the graph‐set notation R₄²(8). This is the first report of a structure of a diprotonated naphthalene‐1,8‐diyldiammonium salt.