Synthesis and 1H and 13C NMR structural analysis of cis‐ and trans‐2‐imino‐1,3‐ and ‐3,1‐perhydrobenzoxazines and their 3‐ and 1‐N‐methyl derivatives

cis‐ and trans‐2‐imino‐1,3‐ and ‐3,1‐perhydrobenzoxazines and the N‐methyl derivatives of the latter were synthesized from the corresponding cyclic 1,3‐amino alcohol with cyanogen bromide. The configurations of the studied compounds were confirmed by ¹H and ¹³C NMR spectra. All trans‐fused compounds exist in biased chair–chair conformations as expected, whereas the cis‐fused 1,3‐benzoxazines attain exclusively the O‐in conformations. The cis‐fused 3,1‐benzoxazines, especially the 1‐methyl‐substituted derivatives, tend to favor the N‐out form, obviously owing to the favorable axial orientation of this N‐methyl. Copyright © 2003 John Wiley & Sons, Ltd.     

Bis­[S‐methyl 3‐(2‐bromo­benzyl­idene)­di­thio­cab­aza­to‐N3,S]­platinum(II)

The Schiff base ligand in the title complex, [Pt(C₉H₈BrN₂S₂)₂], is deprotonated from its tautomeric thiol form and coordinated to Pt^IIvia the mercapto S and β–N atoms. The configuration about Pt^II is a perfect square‐planar, with two equivalent Pt—N [2.023 (3) Å] and Pt—S [2.293 (1) Å] bonds. The phenyl ring is twisted against the coordination moiety Pt1/N1/N1′/S2′/S2 by 31.8 (2)°, due to the steric hindrance induced by ortho‐substituted bulky Br atom.     

The anilinium chloride adduct of 4‐bromo‐N‐phenylbenzene­sulfonamide

The title compound anilinium chloride–4‐bromo‐N‐phenyl­benzene­sulfonamide (1/1), C₆H₈N⁺·Cl⁻·C₁₂H₁₀BrNO₂S, displays a hydrogen‐bonded ladder motif with four independent N—H⋯Cl bonds in which both the NH group of the sulfonamide molecule and the NH₃ group of the anilinium ion [N⋯Cl = 3.135 (3)–3.196 (2) Å and N—H⋯Cl = 151–167°] are involved. This hydrogen‐bonded chain contains two independent R₄²(8) rings and each chloride ion acts as an acceptor of four hydrogen bonds.     

Comparison of the hydrogen‐bond patterns in 2‐amino‐1,3,4‐thiadiazolium hydrogen oxalate, 2‐amino‐1,3,4‐thiadiazole–succinic acid (1/2), 2‐amino‐1,3,4‐thiadiazole–glutaric acid (1/1) and 2‐amino‐1,3,4‐thiadiazole–adipic acid (1/1)

The X‐ray single‐crystal structure determinations of the chemically related compounds 2‐amino‐1,3,4‐thiadiazolium hydrogen oxalate, C₂H₄N₃S⁺·C₂HO₄⁻, (I), 2‐amino‐1,3,4‐thiadiazole–succinic acid (1/2), C₂H₃N₃S·2C₄H₆O₄, (II), 2‐amino‐1,3,4‐thiadiazole–glutaric acid (1/1), C₂H₃N₃S·C₅H₈O₄, (III), and 2‐amino‐1,3,4‐thiadiazole–adipic acid (1/1), C₂H₃N₃S·C₆H₁₀O₄, (IV), are reported and their hydrogen‐bonding patterns are compared. The hydrogen bonds are of the types N—H...O or O—H...N and are of moderate strength. In some cases, weak C—H...O interactions are also present. Compound (II) differs from the others not only in the molar ratio of base and acid (1:2), but also in its hydrogen‐bonding pattern, which is based on chain motifs. In (I), (III) and (IV), the most prominent feature is the presence of an R₂²(8) graph‐set motif formed by N—H...O and O—H...N hydrogen bonds, which are present in all structures except for (I), where only a pair of N—H...O hydrogen bonds is present, in agreement with the greater acidity of oxalic acid. There are nonbonding S...O interactions present in all four structures. The difference electron‐density maps show a lack of electron density about the S atom along the S...O vector. In all four structures, the carboxylic acid H atoms are present in a rare configuration with a C—C—O—H torsion angle of ∼0°. In the structures of (II)–(IV), the C—C—O—H torsion angle of the second carboxylic acid group has the more common value of ∼|180|°. The dicarboxylic acid molecules are situated on crystallographic inversion centres in (II). The Raman and IR spectra of the title compounds are presented and analysed.     

N,N′‐Diethyl‐4‐nitrobenzene‐1,3‐diamine, 2,6‐bis(ethylamino)‐3‐nitrobenzonitrile and bis(4‐ethylamino‐3‐nitrophenyl) sulfone

N,N′‐Diethyl‐4‐nitrobenzene‐1,3‐diamine, C₁₀H₁₅N₃O₂, (I), crystallizes with two independent molecules in the asymmetric unit, both of which are nearly planar. The molecules differ in the conformation of the ethylamine group trans to the nitro group. Both molecules contain intramolecular N—H...O hydrogen bonds between the adjacent amine and nitro groups and are linked into one‐dimensional chains by intermolecular N—H...O hydrogen bonds. The chains are organized in layers parallel to (101) with separations of ca 3.4 Å between adjacent sheets. The packing is quite different from what was observed in isomeric 1,3‐bis(ethylamino)‐2‐nitrobenzene. 2,6‐Bis(ethylamino)‐3‐nitrobenzonitrile, C₁₁H₁₄N₄O₂, (II), differs from (I) only in the presence of the nitrile functionality between the two ethylamine groups. Compound (II) crystallizes with one unique molecule in the asymmetric unit. In contrast with (I), one of the ethylamine groups, which is disordered over two sites with occupancies of 0.75 and 0.25, is positioned so that the methyl group is directed out of the plane of the ring by approximately 85°. This ethylamine group forms an intramolecular N—H...O hydrogen bond with the adjacent nitro group. The packing in (II) is very different from that in (I). Molecules of (II) are linked by both intermolecular amine–nitro N—H...O and amine–nitrile N—H...N hydrogen bonds into a two‐dimensional network in the (10) plane. Alternating molecules are approximately orthogonal to one another, indicating that π–π interactions are not a significant factor in the packing. Bis(4‐ethylamino‐3‐nitrophenyl) sulfone, C₁₆H₁₈N₄O₆S, (III), contains the same ortho nitro/ethylamine pairing as in (I), with the position para to the nitro group occupied by the sulfone instead of a second ethylamine group. Each 4‐ethylamino‐3‐nitrobenzene moiety is nearly planar and contains the typical intramolecular N—H...O hydrogen bond. Due to the tetrahedral geometry about the S atom, the molecules of (III) adopt an overall V shape. There are no intermolecular amine–nitro hydrogen bonds. Rather, each amine H atom has a long (H...O ca 2.8 Å) interaction with one of the sulfone O atoms. Molecules of (III) are thus linked by amine–sulfone N—H...O hydrogen bonds into zigzag double chains running along [001]. Taken together, these structures demonstrate that small changes in the functionalization of ethylamine–nitroarenes cause significant differences in the intermolecular interactions and packing.     

Design of two series of 1:1 cocrystals involving 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine and carboxylic acids

Two series of a total of ten cocrystals involving 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine with various carboxylic acids have been prepared and characterized by single‐crystal X‐ray diffraction. The pyrimidine unit used for the cocrystals offers two ring N atoms (positions N1 and N3) as proton‐accepting sites. Depending upon the site of protonation, two types of cations are possible [Rajam et al. (2017). Acta Cryst. C 73 , 862–868]. In a parallel arrangement, two series of cocrystals are possible depending upon the hydrogen bonding of the carboxyl group with position N1 or N3. In one series of cocrystals, i.e. 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–3‐bromothiophene‐2‐carboxylic acid (1/1), 1 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–5‐chlorothiophene‐2‐carboxylic acid (1/1), 2 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2,4‐dichlorobenzoic acid (1/1), 3 , and 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2‐aminobenzoic acid (1/1), 4 , the carboxyl hydroxy group (–OH) is hydrogen bonded to position N1 (O—H…N1) of the corresponding pyrimidine unit (single point supramolecular synthon). The inversion‐related stacked pyrimidines are doubly bridged by the carboxyl groups via N—H…O and O—H…N hydrogen bonds to form a large cage‐like tetrameric unit with an R₄²(20) graph‐set ring motif. These tetrameric units are further connected via base pairing through a pair of N—H…N hydrogen bonds, generating R₂²(8) motifs (supramolecular homosynthon). In the other series of cocrystals, i.e. 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–5‐methylthiophene‐2‐carboxylic acid (1/1), 5 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–benzoic acid (1/1), 6 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–2‐methylbenzoic acid (1/1), 7 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–3‐methylbenzoic acid (1/1), 8 , 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–4‐methylbenzoic acid (1/1), 9 , and 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–4‐aminobenzoic acid (1/1), 10 , the carboxyl group interacts with position N3 and the adjacent 4‐amino group of the corresponding pyrimidine ring via O—H…N and N—H…O hydrogen bonds to generate the robust R₂²(8) supramolecular heterosynthon. These heterosynthons are further connected by N—H…N hydrogen‐bond interactions in a linear fashion to form a chain‐like arrangement. In cocrystal 1 , a Br…Br halogen bond is present, in cocrystals 2 and 3 , Cl…Cl halogen bonds are present, and in cocrystals 5 , 6 and 7 , Cl…O halogen bonds are present. In all of the ten cocrystals, π–π stacking interactions are observed.     

Hydrogen‐bonding patterns in 3‐alkyl‐3‐hydroxyindolin‐2‐ones

The molecules of racemic 3‐benzoylmethyl‐3‐hydroxyindolin‐2‐one, C₁₆H₁₃NO₃, (I), are linked by a combination of N—H...O and O—H...O hydrogen bonds into a chain of centrosymmetric edge‐fused R₂²(10) and R₄⁴(12) rings. Five monosubstituted analogues of (I), namely racemic 3‐hydroxy‐3‐[(4‐methylbenzoyl)methyl]indolin‐2‐one, C₁₇H₁₅NO₃, (II), racemic 3‐[(4‐fluorobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂FNO₃, (III), racemic 3‐[(4‐chlorobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂ClNO₃, (IV), racemic 3‐[(4‐bromobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂BrNO₃, (V), and racemic 3‐hydroxy‐3‐[(4‐nitrobenzoyl)methyl]indolin‐2‐one, C₁₆H₁₂N₂O₅, (VI), are isomorphous in space group P. In each of compounds (II)–(VI), a combination of N—H...O and O—H...O hydrogen bonds generates a chain of centrosymmetric edge‐fused R₂²(8) and R₂²(10) rings, and these chains are linked into sheets by an aromatic π–π stacking interaction. No two of the structures of (II)–(VI) exhibit the same combination of weak hydrogen bonds of C—H...O and C—H...π(arene) types. The molecules of racemic 3‐hydroxy‐3‐(2‐thienylcarbonylmethyl)indolin‐2‐one, C₁₄H₁₁NO₃S, (VII), form hydrogen‐bonded chains very similar to those in (II)–(VI), but here the sheet formation depends upon a weak π–π stacking interaction between thienyl rings. Comparisons are drawn between the crystal structures of compounds (I)–(VII) and those of some recently reported analogues having no aromatic group in the side chain.     

An optically resolved crystal of thiomalate: (S)‐1‐phenylethanaminium (R)‐thiomalate

The asymmetric unit of the optically resolved title salt, C₈H₁₂N⁺·C₄H₅O₄S⁻, contains a 1‐phenylethanaminium monocation and a thiomalate (3‐carboxy‐2‐sulfanylpropanoate) monoanion. The absolute configurations of the cation and the anion are determined to be S and R, respectively. In the crystal, cation–anion N—H...O hydrogen bonds, together with anion–anion O—H...O and S—H...O hydrogen bonds, construct a two‐dimensional supramolecular sheet parallel to the ab plane. The two‐dimensional sheet is linked with the upper and lower sheets through C—H...π interactions to stack along the c axis.     

Cocrystals of 6‐propyl‐2‐thiouracil: N—H...O versus N—H...S hydrogen bonds

In order to investigate the relative stability of N—H...O and N—H...S hydrogen bonds, we cocrystallized the antithyroid drug 6‐propyl‐2‐thiouracil with two complementary heterocycles. In the cocrystal pyrimidin‐2‐amine–6‐propyl‐2‐thiouracil (1/2), C₄H₅N₃·2C₇H₁₀N₂OS, (I), the `base pair' is connected by one N—H...S and one N—H...N hydrogen bond. Homodimers of 6‐propyl‐2‐thiouracil linked by two N—H...S hydrogen bonds are observed in the cocrystal N‐(6‐acetamidopyridin‐2‐yl)acetamide–6‐propyl‐2‐thiouracil (1/2), C₉H₁₁N₃O₂·2C₇H₁₀N₂OS, (II). The crystal structure of 6‐propyl‐2‐thiouracil itself, C₇H₁₀N₂OS, (III), is stabilized by pairwise N—H...O and N—H...S hydrogen bonds. In all three structures, N—H...S hydrogen bonds occur only within R₂²(8) patterns, whereas N—H...O hydrogen bonds tend to connect the homo‐ and heterodimers into extended networks. In agreement with related structures, the hydrogen‐bonding capability of C=O and C=S groups seems to be comparable.     

Relationships between NMR shifts and interaction energies in biphenyls,alkanes, aza-alkanes,and oxa-alkanes with X─H…H─Y and X─H…Z (X,Y = C or N; Z = N or O) hydrogen bonding

Hydrogen–hydrogen C─H^…H─C bonding between the bay-area hydrogens in biphenyls, and more generally in congested alkanes, very strained polycyclic alkanes, and cis-2-butene, has been investigated by calculation of proton nuclear magnetic resonance (NMR) shifts and atom–atom interaction energies. Computed NMR shifts for all protons in the biphenyl derivatives correlate very well with experimental data, with zero intercept, unit slope, and a root mean square deviation of 0.06 ppm. For some congested alkanes, there is generally good agreement between computed values for a selected conformer and the experimental data, when it is available. In both cases, the shift of a given proton or pair of protons tends to increase with the corresponding interaction energy. Computed NMR shift differences for methylene protons in polycyclic alkanes, where one is involved in a very short contact (“in”) and the other is not (“out”), show a rough correlation with the corresponding C─H^…H─C exchange energies. The “in” and “in,in” isomers of selected aza- and diaza-cycloalkanes, respectively, are X─H^…H─N hydrogen bonded, whereas the “out” and “in,out” isomers display X─H^…N hydrogen bonds (X = C or N). Oxa-alkanes and the “in” isomers of aza–oxa-alkanes are X─H^…O hydrogen bonded. There is a very good general correlation, including both N─H^…H─Y (Y = C or N) and N─H^…Z (Z = N or O) interactions, for NH proton shifts against the exchange energy. For “in” CH protons, the data for the different C─H^…H─Y and C─H^…Z interactions are much more dispersed and the overall shift/exchange energy correlation is less satisfactory.     

Supramolecular hydrogen‐bonding patterns in the organic–inorganic hybrid compound bis(4‐amino‐5‐chloro‐2,6‐dimethylpyrimidinium) tetrathiocyanatozinc(II)–4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–water (1/2/2)

Zinc thiocyanate complexes have been found to be biologically active compounds. Zinc is also an essential element for the normal function of most organisms and is the main constituent in a number of metalloenzyme proteins. Pyrimidine and aminopyrimidine derivatives are biologically very important as they are components of nucleic acids. Thiocyanate ions can bridge metal ions by employing both their N and S atoms for coordination. They can play an important role in assembling different coordination structures and yield an interesting variety of one‐, two‐ and three‐dimensional polymeric metal–thiocyanate supramolecular frameworks. The structure of a new zinc thiocyanate–aminopyrimidine organic–inorganic compound, (C₆H₉ClN₃)₂[Zn(NCS)₄]·2C₆H₈ClN₃·2H₂O, is reported. The asymmetric unit consist of half a tetrathiocyanatozinc(II) dianion, an uncoordinated 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidinium cation, a 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine molecule and a water molecule. The Zn^II atom adopts a distorted tetrahedral coordination geometry and is coordinated by four N atoms from the thiocyanate anions. The Zn^II atom is located on a special position (twofold axis of symmetry). The pyrimidinium cation and the pyrimidine molecule are not coordinated to the Zn^II atom, but are hydrogen bonded to the uncoordinated water molecules and the metal‐coordinated thiocyanate ligands. The pyrimidine molecules and pyrimidinium cations also form base‐pair‐like structures with an R₂²(8) ring motif via N—H…N hydrogen bonds. The crystal structure is further stabilized by intermolecular N—H…O, O—H…S, N—H…S and O—H…N hydrogen bonds, by intramolecular N—H…Cl and C—H…Cl hydrogen bonds, and also by π–π stacking interactions.     

DFT 1H–1H coupling constants in the conformational analysis and stereoisomeric differentiation of 6‐heptenyl‐2H‐pyran‐2‐ones: configurational reassignment of synargentolide A

Density functional theory (DFT) ¹H–¹H NMR coupling constant calculations, including solvation parameters with the polarizable continuum model B3LYP/DGDZVP basis set together with the experimental values measured by spectral simulation, were used to predict the configuration of hydroxylated 6‐heptenyl‐5,6‐dihydro‐2H‐pyran‐2‐ones 1 , 2 , 4 , and 7 , allowing epimer differentiation. Modeling of these flexible compounds requires the inclusion of solvation models that account for stabilizing interactions derived from intramolecular and intermolecular hydrogen bonds, in contrast with peracetylated derivatives ( 3 , 5 , and 6 ) in which the solvation consideration can be omitted. Using this DFT NMR integrated approach as well as spectral simulation, the configurational reassignment of synargentolide A ( 8 ) was accomplished by calculations in the gas phase among four possible diastereoisomers ( 8–11 ). Calculated ³J_H,H values established its configuration as 6R‐[4′S,5′S,6′S‐(triacetyloxy)‐2E‐heptenyl]‐5,6‐dihydro‐2H‐pyran‐2‐one ( 8 ), in contrast with the incorrect 6R,4′R,5′R,6′R‐diastereoisomer previously proposed by synthesis ( 12 ). Application of this approach increases the probability for successful enantiospecific total syntheses of flexible compounds with multiple chiral centers. Copyright © 2014 John Wiley & Sons, Ltd.     

Bis(adamantan‐1‐aminium) tetrachloridozincate(II) 18‐crown‐6 monohydrate clathrate

The structure of the title compound [systematic name: bis(adamantan‐1‐aminium) tetrachloridozincate(II)–1,4,7,10,13,16‐hexaoxacyclooctadecane–water (1/1/1)], (C₁₀H₁₈N)₂[ZnCl₄]·C₁₂H₂₄O₆·H₂O, consists of supramolecular rotator–stator assemblies and ribbons of hydrogen bonds parallel to [010]. The assemblies are composed of one protonated adamantan‐1‐aminium cation and one crown ether molecule (1,4,7,10,13,16‐hexaoxacyclooctadecane) to give an overall [(C₁₀H₁₈N)(18‐crown‐6)]⁺ cation. The –NH₃⁺ group of the cation nests in the crown and links to the crown‐ether O atoms through N—H...O hydrogen bonds. The 18‐crown‐6 ring adopts a pseudo‐C_3v conformation. The second adamantan‐1‐aminium forms part of ribbons of adamantan‐1‐aminium–water–tetrachloridozincate units which are interconnected by O—H...Cl, N—H...O and N—H...Cl hydrogen bonds via three different continuous rings with R₅⁴(12), R₄³(10) and R₃³(8) motifs.     

Supramolecular hydrogen‐bonding patterns in two cocrystals of the N(7)–H tautomeric form of N6‐benzoyladenine: N6‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (1/1) and N6‐benzoyladenine–DL‐tartaric acid (1/1)

Two novel cocrystals of the N(7)—H tautomeric form of N⁶‐benzoyladenine (BA), namely N⁶‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (3HPA) (1/1), C₁₂H₉N₅O·C₆H₅NO₃, (I), and N⁶‐benzoyladenine–DL‐tartaric acid (TA) (1/1), C₁₂H₉N₅O·C₄H₆O₆, (II), are reported. In both cocrystals, the N⁶‐benzoyladenine molecule exists as the N(7)—H tautomer, and this tautomeric form is stabilized by intramolecular N—H...O hydrogen bonding between the benzoyl C=O group and the N(7)—H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson–Crick face of BA (N6—H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N—H...O and O—H...N hydrogen bonds, generating a ring‐motif heterosynthon [graph set R₂²(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N—H...O and O—H...O hydrogen bonds, generating a different heterosynthon [graph set R₂²(4)]. Both crystal structures are further stabilized by π–π stacking interactions.     

[N,N′‐Bis(3‐aminopropyl)ethylenediamine‐κ4N,N′,N′′,N′′′](trithiocyanurato‐κ2N,S)zinc(II) ethanol solvate

In the crystal structure of the title compound, [N,N′‐bis(3‐­amino­propyl)­ethyl­enedi­amine‐κ⁴N,N′,N′′,N′′′][1,3,5‐triazine‐2,4,6(1H,3H,5H)‐tri­thionato(2−)‐κ²N,S]­zinc(II) ethanol sol­vate, [Zn(C₈H₂₂N₄)₂(C₃HN₃S₃)]·C₂H₆O, the Zn^II atom is octa­hedrally coordinated by four N atoms [Zn—N = 2.104 (2)–2.203 (2) Å] of a tetradentate N‐donor N,N′‐bis(3‐­amino­propyl)­ethyl­enedi­amine (bapen) ligand and by two S and N atoms [Zn—S = 2.5700 (7) Å and Zn—N = 2.313 (2) Å] of a tri­thio­cyanurate(2−) (ttcH²⁻) dianion bonded as a bidentate ligand in a cis configuration. The crystal structure of the compound is stabilized by a network of hydrogen bonds.     

Supramolecular architectures in cytosinium 6‐chloronicotinate monohydrate and 5‐bromo‐6‐methylisocytosinium hydrogen sulfate

Aminopyrimidine derivatives are biologically important as they are components of nucleic acids and drugs. The crystals of two new salts, namely cytosinium 6‐chloronicotinate monohydrate, C₄H₆N₃O⁺·C₆H₃ClNO₂⁻·H₂O, ( I ), and 5‐bromo‐6‐methylisocytosinium hydrogen sulfate (or 2‐amino‐5‐bromo‐4‐oxo‐6‐methylpyrimidinium hydrogen sulfate), C₅H₇BrN₃O⁺·HSO₄⁻, ( II ), have been prepared and characterized by single‐crystal X‐ray diffraction. The pyrimidine ring of both compounds is protonated at the imine N atom. In hydrated salt ( I ), the primary R₂²(8) ring motif (supramolecular heterosynthon) is formed via a pair of N—H…O(carboxylate) hydrogen bonds. The cations, anions and water molecule are hydrogen bonded through N—H…O, N—H…N, O—H…O and C—H…O hydrogen bonds, forming R₂²(8), R₃²(7) and R₅⁵(21) motifs, leading to a hydrogen‐bonded supramolecular sheet structure. The supramolecular double sheet structure is formed via water–carboxylate O—H…O hydrogen bonds and π–π interactions between the anions and the cations. In salt ( II ), the hydrogen sulfate ions are linked via O—H…O hydrogen bonds to generate zigzag chains. The aminopyrimidinium cations are embedded between these zigzag chains. Each hydrogen sulfate ion bridges two cations via pairs of N—H…O hydrogen bonds and vice versa, generating two R₂²(8) ring motifs (supramolecular heterosynthon). The cations also interact with one another via halogen–halogen (Br…Br) and halogen–oxygen (Br…O) interactions.     

Supramolecular Structures with the 2‐Propyl‐4,5‐dicarboxy‐1H‐imidazole Ligand: Hydrothermal Synthesis,Structures, and Photoluminescence

Self‐assembly of the rigid organic ligand 2‐propyl‐4,5‐dicarboxy‐1H‐imidazole ( L ) with different metal ions (Zn²⁺, Ni²⁺, Cu²⁺, Cd²⁺) led to four new complexes, namely, [M( L )(phen)] [M = Zn ( 1 ); Ni ( 2 ); Cd ( 3 )] and [Cu( L )( 4 )] (phen = 1,10‐phenanthroline). Their structures were determined by single‐crystal X‐ray diffraction analyses, and they were further characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis. Whereas compounds 1 , 2 , and 3 are discrete units, hydrogen‐bonding interactions play a vital role in these complexes. Compounds 1 and 2 form one‐dimensional (1D) and two‐dimensional (2D) structures through hydrogen‐bondinginteractions with helical character. In 1 , the hydrogen bonds (O–H ··· O) alternately bridge the M^II cations of the discrete units to form a one‐dimensional (1D) infinite helical chain. Complex 2 forms a 2D helical layer through parallel hydrogen bonds (N/O–H ··· O/N) between two adjacent helical chains. In 3 , the hydrogen bonds (N–H ··· O) connect adjacent discrete units into a ten‐membered ring with extension into a one‐dimensional double‐chain supramolecular structure. Complex 4 is a two‐dimensional gridlike (4,4) topological layer which is extended to a 3D network by hydrogen bonding. The solid‐state fluorescence spectrum of complex 3 was determined.     

The Structure of Bis[N‐6‐aminopyridyl‐N‐(1S)‐(+)‐10‐camphorsulfonylamino]palladium in the Solid State and in Solution

The complex, bis[N‐6‐aminopyridyl‐N‐(1S)‐(+)‐10‐camphorsulfonylamino]palladium, Pd[(S)‐APCS]₂, 1 , was prepared by reaction of 2‐[(1S)‐(+)‐10‐camphorsulfonamino]‐6‐aminopyridine with PdCl₂ in THF. Complex 1 has been characterized by spectroscopic methods and its structure has been determined by X‐ray crystallography. Crystal data: space group C2, a= 16.082 (2), b = 17.104 (2), c = 13.051 (2)Å, β = 99.95 (1)°, V = 3535.9 (8) ų, Z = 2 with final residuals R1 = 0.0491 and wR2 = 0.0944. Two independent molecules, (S,S)‐Pd[(S)‐APCS]2, 1a , and (R,R)‐Pd[(S)‐APCS]2, 1b , were found in each asymmetric unit, which exchange to each other via a series of nitrogen inversion and C‐C bond rotation. The inversion energy (ΔGc₁^≠) and the energy barrier (δGc₂^≠) were 11.5 ± 0.1 Kcal mol^?1 at 246 K and 9.8 ± 0.1 Kcal mol^?1 at 199 K, respectively, calculated by dynamic NMR data.     

1H{15N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and 1H, 13C and 15N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

The ¹H{¹⁵N} NMR spectrum of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]‐pyrimidine ( 3 ) was measured by GHMQC, unambiguously assigned and compared with the spectra of 1,2,4‐triazolo[1,5‐a]pyrimidine ( 1 ) and 5,7‐dimethyl‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 2 ). A series of Au(III) chloride complexes of general formula AuLCl₃, where L = 1 , 2 , 3 , was synthesized and studied by ¹HH{¹⁵N} GHMQC and ¹H{¹³C} GHMBC. Low‐frequency shifts of 72–74 ppm (¹⁵N) and 5–6 ppm (¹³C) were observed upon complexation by Au(III) ions for the coordination site N‐3 and adjacent C‐2, C‐3a atoms, respectively. The ¹³C signals of C‐5, C‐6, C‐7 and the ¹H resonances of H‐2, H‐6 were shifted to higher frequency. Comparison with analogous Pd(II), Pt(II) and Pt(IV) complexes revealed that in the case of Au(III) coordination the ¹⁵N shifts were relatively smaller, whereas those for ¹³C and ¹H were larger. Copyright © 2002 John Wiley & Sons, Ltd.     

2,4‐Diamino‐6‐methyl‐1,3,5‐triazin‐1‐ium trifluoroacetate

Crystals of the title compound, C₄H₈N₅⁺·C₂F₃O₂⁻, are built up of singly protonated 2,4‐diamino‐6‐methyl‐1,3,5‐triazin‐1‐ium cations and trifluoroacetate anions. The CF₃ group of the anion is disordered. The oppositely charged ions interact via almost linear N—H...O hydrogen bonds, forming a CF₃COO⁻...C₄H₈N₅⁺ unit. Two units related by an inversion centre interact through a pair of N—H...N hydrogen bonds, forming planar (CF₃COO⁻...C₄H₈N₅⁺...C₄H₈N₅⁺·CF₃COO⁻) aggregates that are linked by a pair of N—H...O hydrogen bonds into chains running along the c axis.