Hydro­gen‐bonded adducts of ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol): a finite cyclic 1:1 adduct with 2,2′‐dipyridyl­amine

In ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–2,2′‐dipyridyl­amine (1/1), [Fe(C₁₈H₁₅O)₂]·C₁₀H₉N₃, (I), there is an intramolecular O—H?O hydrogen bond [H?O 2.03 Å, O?O 2.775 (2) Å and O—H?O 147°] in the ferrocenediol component, and the two neutral molecular components are linked by one O—H?N hydrogen bond [H?N 1.96 Å, O?N 2.755 (2) Å and O—H?N, 157°] and one N—H?O hydrogen bond [H?O 2.26 Å, N?O 3.112 (2) Å and N—H?O 164°] forming a cyclic R(8) motif. One of the pyridyl N atoms plays no part in the intermolecular hydrogen bonding, but participates in a short intramolecular C—H?N contact [H?N 2.31 Å, C?N 2.922 (2) Å and C—H?N 122°].     

(E)‐2‐Methyl‐5‐(1‐naphthyl­methyl)­cinnamic acid

The title compound, C₂₁H₁₈O₂, crystallized in the centrosymmetric space group P2₁/n with one mol­ecule in the asymmetric unit. There is a single hydrogen bond, with an O_donor?O_acceptor distance of 2.624 (2) Å, which forms a cyclic dimer about a center of symmetry. The carboxyl group O atoms are ordered, while the carboxyl‐H atom is disordered. A single leading intermolecular C—H?O interaction has an H?O distance of 2.68 Å and a C—H?O angle of 178°; this interaction forms chains. Taken together with the hydrogen bond, it generates chains and rings. Structural comparisons are made with trans‐cinnamic acid and with 4‐methyl‐trans‐cinnamic acid.     

Iridium‐Catalyzed Reductive Carbon–Carbon Bond Cleavage Reaction on a Curved Pyridylcorannulene Skeleton

The cleavage of C? C bonds in π‐conjugated systems is an important method for controlling their shape and coplanarity. An efficient way for the cleavage of an aromatic C? C bond in a typical buckybowl corannulene skeleton is reported. The reaction of 2‐pyridylcorannulene with a catalytic amount of IrCl₃?n H₂O in ethylene glycol at 250 °C resulted in a structural transformation from the curved corannulene skeleton to a strain‐free flat benzo[ghi]fluoranthene skeleton through a site‐selective C? C cleavage reaction. This cleavage reaction was found to be driven by both the coordination of the 2‐pyridyl substituent to iridium and the relief of strain in the curved corannulene skeleton. This finding should facilitate the design of carbon nanomaterials based on C? C bond cleavage reactions.     

Conformation of cationic N,N‐di­methyl­glycine in di­methyl­glycinium tri­fluoro­acetate

In the title compound, C₄H₁₀NO₂⁺·C₂F₃O₂^?, the main N—C—COOH skeleton of the protonated amino acid is nearly planar. The C=O/C—N and C=O/O—H bonds are syn and the two methyl groups are gauche to the methyl­ene H atoms. The conformation of the cation in the crystal is compared to that given by ab initio calculations (Hartree–Fock, self‐consistent field molecular‐orbital theory). The tri­fluoro­acetate anion has the typical staggered conformation with usual bond distances and angles. The cation and anion form dimers through a strong O—H?O hydrogen bond which are further interconnected in infinite zigzag chains running parallel to the a axis by N—H?O bonds. Weaker C—H?O interactions involving the methyl groups and the carboxy O atoms of the cation occur between the chains.     

4,8‐Di­methoxy‐1‐naphthalene­methanol

The title compound, C₁₃H₁₄O₃, crystallized in the centrosymmetric space group C2/c with one mol­ecule as the asymmetric unit. Each hydroxyl O atom is involved in hydrogen bonds with two other hydroxyl O atoms. The resulting chains of interactions propagate along [001]. In these interactions, the hydroxyl H atoms are disordered and the O?O distances are 2.648 (2) and 2.698 (2) Å. Two leading intermolecular C—H?O interactions have H?O distances of 2.80 and 2.84 Å and C—H?O angles of 136 and 144°; these interactions form chain and ring patterns. Taken together with the hydrogen bonds, they result in a three‐dimensional network.     

Zwitterionic pyrrolidine‐2,2‐diylbis(phosphonic acid) at 100, 150 and 293 K

The title compound, C₄H₁₁NO₆P₂, reveals a two‐dimensional network of P—O—H?O=P and N—H?O=P hydrogen‐bond interactions, forming molecular slabs parallel with the (010) plane. One O—H?O interaction is distinct within these sets: whilst forming the shortest intermolecular hydrogen bond, it possesses a short P—O(H) bond of 1.5291 (10) Å. Weak C—H?O contacts link individual stacks to produce a three‐dimensional array. The compound is zwitterionic: one H atom from a P—O—H group has transferred to the pyrrolidine ring N atom.     

Asymmetric Desymmetrization via Metal‐Free C−F Bond Activation: Synthesis of 3,5‐Diaryl‐5‐fluoromethyloxazolidin‐2‐ones with Quaternary Carbon Centers

We disclose the first asymmetric activation of a non‐activated aliphatic C?F bond in which a conceptually new desymmetrization of 1,3‐difluorides by silicon‐induced selective C?F bond scission is a key step. The combination of a cinchona alkaloid based chiral ammonium bifluoride catalyst and N,O‐bis(trimethylsilyl)acetoamide (BSA) as the silicon reagent enabled the efficient catalytic cycle of asymmetric C_sp3?F bond cleavage under mild conditions with high enantioselectivities. The ortho effect of the aryl group at the prostereogenic center is remarkable. This concept was applied for the asymmetric synthesis of promising agrochemical compounds, 3,5‐diaryl‐5‐fluoromethyloxazolidin‐2‐ones bearing a quaternary carbon center.     

μ‐Acetato‐1:2κ2O:O′‐diacetato‐1κ2O,O′;2κO‐bis(di‐2‐pyridylamine)‐1κ2N,N′;2κ2N,N′‐isothiocyanato‐2κN‐dicopper(II)

In the title dinuclear acetate‐bridged complex, [Cu₂(C₂H₃O₂)₃(NCS)(C₁₀H₉N₃)₂], the two Cu atoms are five‐coordinated, with a basal plane consisting of two N atoms of a di‐2‐pyridylamine (dpyam) ligand and two O atoms of two different acetate ligands. The axial positions of these Cu atoms are coordinated to N and O atoms from thio­cyanate and acetate mol­ecules, respectively, leading to a distorted square‐pyramidal geometry with τ values of 0.30 and 0.22. Both Cu^II ions are linked by an acetate group in the equatorial–equatorial positions and have syn–anti bridging configurations. Hydrogen‐bond inter­actions between the amine H atom and the coordinated and uncoordinated O atoms of the acetate anions generate an infinite one‐dimensional chain.     

Comprehensive Analysis of DNA Strand Breaks at the Guanosine Site Induced by Low‐Energy Electron Attachment

To elucidate the role of guanosine in DNA strand breaks caused by low‐energy electrons (LEEs), theoretical investigations of the LEE attachment‐induced C? O σ‐bonds and N‐glycosidic bond breaking of 2′‐deoxyguanosine‐3′,5′‐diphosphate (3′,5′‐dGMP) were performed using the B3LYP/DZP++ approach. The results reveal possible reaction pathways in the gas phase and in aqueous solutions. In the gas phase LEEs could attach to the phosphate group adjacent to the guanosine to form a radical anion. However, the small vertical detachment energy (VDE) of the radical anion of guanosine 3′,5′‐diphosphate in the gas phase excludes either C? O bond cleavage or N‐glycosidic bond breaking. In the presence of the polarizable surroundings, the solvent effects dramatically increase the electron affinities of the 3′,5′‐dGDP and the VDE of 3′,5′‐dGDP^?. Furthermore, the solvent–solute interactions greatly reduce the activation barriers of the C? O bond cleavage to 1.06–3.56 kcal mol^?1. These low‐energy barriers ensure that either C_5′? O_5′ or C_3′? O_3′ bond rupture takes place at the guanosine site in DNA single strands. On the other hand, the comparatively high energy barrier of the N‐glycosidic bond rupture implies that this reaction pathway is inferior to C? O bond cleavage. Qualitative agreement was found between the theoretical sequence of the bond breaking reaction pathways in the PCM model and the ratio for the corresponding bond breaks observed in the experiment of LEE‐induced damage in oligonucleotide tetramer CGTA. This concord suggests that the influence of the surroundings in the thin solid film on the LEE‐induced DNA damage resembles that of the solvent.     

Hydro­gen bonds and C—H⃛O interactions in N‐(2‐hydroxy‐1,1‐dimethyl­ethyl)benzamide at 150 K

The title compound, C₁₁H₁₅NO₂, crystallized in the centrosymmetric space group P2₁/n with one mol­ecule in the asymmetric unit. There is a single intermolecular hydrogen bond, in which the N_donor?O_acceptor distance is 3.0374 (11) Å and the N—H?O angle is 171.0 (12)°. The single intramol­ecular hydrogen bond has an O_donor?O_acceptor distance of 2.6279 (11) Å and an O—H?O angle of 161.8 (14)°. The four leading intermolecular C—H?O interactions have H?O distances ranging from 2.52 to 2.65 (2) Å and C—H?O angles ranging from 125.2 (9) to 143°. Chains of interactions form two‐dimensional networks.     

4‐Fluoro‐2‐(phospho­no­methyl)­benzene­sulfonic acid monohydrate

The title compound, C₇H₈FO₆PS·H₂O, contains both phospho­nic and sulfonic acid functionalities. An extensive network of O—H?O hydrogen bonds is present in the crystal structure. The three acidic protons are associated with the phospho­nate group. Two protons experience typical hydrogen‐bond contacts with the sulfonate‐O atoms, while the third has a longer covalent bond of 1.05 (3) Å to the phospho­nate‐O atom and a short hydrogen‐bond contact of 1.38 (3) Å to the water O atom (all O—H?O angles are in the range 162–175°). The sulfonate group is positioned so that one S—O bond is nearly coplanar with the phenyl ring [torsion angle O—S—C—C ?8.6 (2)°]. The phospho­nate group is oriented approximately perpendicular to the ring [torsion angle P—C—C—C 99.2 (2)°] with one P—O bond anti to the benzyl C—C bond. The mol­ecules pack in layers in the b–c plane with the water mol­ecules in between adjacent pairs of inverted layers.     

N‐tert‐Butyl‐N′‐(5,7‐di­methyl‐1,8‐naphthyridin‐2‐yl)­urea

The title compound, C₁₅H₂₀N₄O, has been synthesized as an AADD recognition unit for quadruple hydrogen bonds. All non‐H atoms of the mol­ecule apart from two methyl groups of the tert‐butyl group lie in a common plane. An intramolecular hydrogen bond is formed connecting two N atoms. In the solid state, the title compound crystallizes as a centrosymmetric dimer connected by N—H?O=C interactions with an N?O distance of 2.824 (2) Å.     

Bis(2‐amino­pyridine‐N)­bis­(benzoato‐O)­zinc

The crystal structure of the title compound, [Zn‐(C₇H₅O₂)₂(C₅H₆N₂)₂], is built of monomeric [Zn(2‐apy)₂(OBz)₂] mol­ecules (apy is amino­pyridine and OBz is benzoate). The Zn atom lies on a twofold symmetry axis and adopts a slightly distorted tetrahedral coordination. The Zn?O distances to the non‐coordinated O atoms are long at 2.872 (3) Å. Each non‐ligating carbonyl O atom of the benzoate anion accepts one intramolecular and one intermolecular hydrogen bond from the amino group. The mol­ecules form a chain along the c axis through intermolecular N—H?O hydrogen bonds between the amino and carboxyl groups.     

4,4′‐Bis(2,2,2‐trifluoroethoxymethyl)‐2,2′‐bipyridine

As part of a homologous series of novel polyfluorinated bipyridyl (bpy) ligands, the title compound, C₁₆H₁₄F₆N₂O₂, contains the smallest fluorinated group, viz. CF₃. The molecule resides on a crystallographic inversion centre at the mid‐point of the pyridine C_ipso—C_ipso bond. Therefore, the bpy skeleton lies in an anti conformation to avoid repulsion between the two pyridyl N atoms. Weak intramolecular C—H...N and C—H...O interactions are observed, similar to those in related polyfluorinated bpy–metal complexes. A π–π interaction is observed between the bpy rings of adjacent molecules and this is probably a primary driving force in crystallization. Weak intermolecular C—H...N hydrogen bonding is present between one of the CF₃CH₂– methylene H atoms and a pyridyl N atom related by translation along the [010] direction, in addition to weak benzyl‐type C—H...F interactions to atoms of the terminal CF₃ group. It is of note that the O—CH₂CF₃ bond is almost perpendicular to the bpy plane.     

Hydro­gen bonds and C—H⋯O interactions in 2,2′‐dimethoxybiphenyl‐5,5′‐dimethanol at 150 K

The title compound, C₁₆H₁₈O₄, crystallized in the centrosymmetric space group P2₁/c with one mol­ecule in the asymmetric unit. The two hydroxyl‐H atoms are ordered, and are involved in intermolecular hydrogen bonds with O_donor?O_acceptor distances of 2.761 (1) and 2.699 (1) Å, and O—H?O angles of 157 (2) and 168 (2)°. Seven leading intermolecular C—H?O interactions have H?O distances ranging from 2.41 to 2.76 Å and C—H?O angles ranging from 125 to 170°. The hydrogen bonds and C—H?O interactions form chain and ring patterns, resulting in a richly three‐dimensional network. The bi­phenyl twist angle is 67.2 (1)°.     

An X‐ray crystallographic and density functional theory study of (3Z)‐4‐(5‐ethylsulfonyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one and (3Z)‐4‐(5‐tert‐butyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one

The Schiff base enaminones (3Z)‐4‐(5‐ethylsulfonyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one, C₁₃H₁₇NO₄S, (I), and (3Z)‐4‐(5‐tert‐butyl‐2‐hydroxyanilino)pent‐3‐en‐2‐one, C₁₅H₂₁NO₂, (II), were studied by X‐ray crystallography and density functional theory (DFT). Although the keto tautomer of these compounds is dominant, the O=C—C=C—N bond lengths are consistent with some electron delocalization and partial enol character. Both (I) and (II) are nonplanar, with the amino–phenol group canted relative to the rest of the molecule; the twist about the N(enamine)—C(aryl) bond leads to dihedral angles of 40.5 (2) and −116.7 (1)° for (I) and (II), respectively. Compound (I) has a bifurcated intramolecular hydrogen bond between the N—H group and the flanking carbonyl and hydroxy O atoms, as well as an intermolecular hydrogen bond, leading to an infinite one‐dimensional hydrogen‐bonded chain. Compound (II) has one intramolecular hydrogen bond and one intermolecular C=O...H—O hydrogen bond, and consequently also forms a one‐dimensional hydrogen‐bonded chain. The DFT‐calculated structures [in vacuo, B3LYP/6‐311G(d,p) level] for the keto tautomers compare favourably with the X‐ray crystal structures of (I) and (II), confirming the dominance of the keto tautomer. The simulations indicate that the keto tautomers are 20.55 and 18.86 kJ mol⁻¹ lower in energy than the enol tautomers for (I) and (II), respectively.     

Hydro­gen bonding and C—H⃛O interactions in 4‐phenanthrenemethanol at 150 K

The title compound, C₁₅H₁₂O, crystallizes in the centrosymmetric space group I4₁/a with one mol­ecule in the asymmetric unit. In the single hydrogen bond, the H atom is ordered, the O_D?O_A distance is 2.788 (1) Å and the O—H?O angle is 176 (1)°. Each hydroxyl group forms hydrogen bonds with two other hydroxyl groups and the resulting chains of interactions, in four non‐linked subsets of mol­ecules, propagate along [001]. The single leading intermolecular C—H?O interaction has an H?O distance of 2.81 Å and a C—H?O angle of 140°; the single leading intramolecular C—H?O interaction has an H?O distance of 2.24 Å and a C—H?O angle of 152°. The phenanthrene core is less nearly planar in this structure than in the room temperature structure of phenanthrene‐4‐carboxylic acid.     

Hydro­gen‐bonded adducts of ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol): monomeric and dimeric 1:1 adducts with 1,2‐bis(4‐pyridyl)­ethane and 1,2‐­diamino­ethane

In ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–4,4′‐ethyl­enedi­pyridine (1/1), [Fe(C₁₈H₁₅O)₂]·C₁₂H₁₂N₂, there is an intra­molecular O—H?O hydrogen bond in the ferrocenediol component and a single O—H?N hydrogen bond linking the two components into a finite monomeric adduct. Ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–ethyl­enedi­amine (1/1), [Fe(C₁₈H₁₅O)₂]·C₂H₈N₂, crystallizes with Z′ = 2 in space group P, and there are two independent four‐component aggregates in the structure, both of which are centrosymmetric. In the first type of aggregate, the molecular components are linked by O—H?N and N—H?O hydrogen bonds, in which both di­amine N atoms participate; in the second type of aggregate, the di­amine component is disordered over two sets of sites, but only one N atom is involved in the hydrogen bonding.     

Racemic dipeptide glycyl‐dl‐leucine at 120 K

The structure of glycyl‐dl ‐leucine, C₈H₁₆N₂O₃, has been determined at 120 K by single‐crystal X‐ray diffraction. In addition to three N—H?O‐type hydrogen bonds of the positively charged RNH₃⁺ group of the zwitterionic mol­ecule, an intermolecular N—H?O contact exists between the peptide bond and the carboxyl­ate group. Four hydrogen‐bond cycles were identified, giving a complex pattern.     

Potassium bis­(carbonato‐O,O′)(ethylenedi­amine‐N,N′)­cobaltate(III) monohydrate at 173 K

The title salt, K[Co(C₂H₈N₂)(CO₃)₂]·H₂O, consists of a distorted octahedral cobalt complex anion and a seven‐coordinate potassium cation. Both metal atoms have crystallographic twofold symmetry, one C₂ axis passing through the Co atom and C—C bond, and another along a short K—O (water) bond of 2.600 Å (corrected for libration). The carbonate is bidentate to both cobalt and potassium and the water forms a hydrogen bond to a carbonate O atom.