N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and inter... more N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and intermolecular hydrogen bonds that leads to cavitand-like structures. Depending on the upper-rim substituents, self-inclusion was observed in solution and in the solid state. The self-inclusion can be disrupted at higher temperatures, whereas in the presence of small guests the self-included dimers spontaneously reorganize to 1:1 host-guest complexes. These host compounds show an interesting ability to bind a series of N-alkyl acetamide guests through intermolecular hydrogen bonds involving the carbonyl oxygen (C=O) atoms and the amide (NH) groups of the guests, the chloride anions (Cl(-)) and ammonium (NH2(+)) cations of the hosts, and also through CH⋅⋅⋅π interactions between the hosts and guests. The self-included and host-guest complexes were studied by single-crystal X-ray diffraction, NMR titration, and mass spectrometry.
Single crystal X-ray structures (monoclinic space group P21) for methyl 3-oxo-5b-cholan-24-oate a... more Single crystal X-ray structures (monoclinic space group P21) for methyl 3-oxo-5b-cholan-24-oate and methyl 3,12-dioxo-5b-cholan-24-oate have been solved and compared with HF/6-31G* optimised structures. In the crystalline packings the side chains are connected with weak OC(sp3)H• • •O-type of interactions between C25–H and C24–O–C25 and the keto ends with weak C(sp3)H• • •O=C-type of interactions between C4–H and O=C3. The orientations of the side chains, which steric configurations are of great importance to the biological activity of the molecules, are compared with the experimental structure of methyl 3a-hydroxy-5b-cholan-24-oate. Probable reasons for the observed differences are discussed. In addition, 13C and 17O NMR chemical shifts of methyl 3-oxo-5b-cholan-24-oate and methyl 3,12-dioxo-5b-cholan-24-oate as well as the epimeric methyl 3a-hydroxy-5b-cholan-24-oate and methyl 3b-hydroxy-5b-cholan-24-oate have been calculated (DFT/B3LYP/6-311G*) and compared with the experimental...
The 1H and 13C NMR chemical shifts for six toxaphene congeners: 2-exo,3-endo,6-exo,8,9,10-hexachl... more The 1H and 13C NMR chemical shifts for six toxaphene congeners: 2-exo,3-endo,6-exo,8,9,10-hexachloro- (1), 2-exo,3-endo,5-exo,9,9,10, 10-heptachloro- (2), 2-exo,3-endo,6-exo,8,9,10,10-heptachloro- (3), 2-exo,3-endo,5-exo,6-endo,8,9,10-heptachloro- (4), 2-exo,3-endo,5-exo, 6-endo,8,9,9,10-octachlorobornane (5) and 2,5-endo,6-exo,8,9,9,10,10-octachloro-2-bornene (6) are reported. Their chemical shift assignments have been obtained by means of Pulsed Field Gradient (PFG) Double Quantum Filtered (DQF) 1H,1H correlation spectroscopy (COSY), PFG 1H,13C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG 1H,13C Heteronuclear Multiple Bond Correlation (HMBC) experiments. A single crystal X-ray structural analysis was made for compounds 1, 3, 4 and 6. The prevalences of two octachlorobornene rotamers (6a,6b) were elucidated by ab initio MO method and single point DFT/GIAO calculations for 13C chemical shifts. Theoretical calculations proved that the single crystal structure of 6 correspo...
Acta Crystallographica Section E Structure Reports Online
The title compound, C(33)H(3)F(20)N(3)O(4), is a highly fluorinated organic imide that was isolat... more The title compound, C(33)H(3)F(20)N(3)O(4), is a highly fluorinated organic imide that was isolated as an unexpected product from the reaction of 2,6-diamino-pyridine with 2,3,4,5,6-penta-fluoro-benzoyl chloride in a 1:2 molar ratio. The mol-ecule is located on a twofold axis and one of its symmetry-independent 2,3,4,5,6-penta-fluoro-benzoyl groups is disordered over two sets of sites, the occupancy of the major component being 0.773 (3). In the major component, the dihedral angle between the perfluoro-phenyl groups is 63.64 (10)°, and these groups form dihedral angles of 67.14 (7) and 21.1 (2)° with the pyridine core. Short inter-molecular C-H⋯O and C-H⋯N contacts are found in the crystal structure.
Acta Crystallographica Section E Structure Reports Online
The title compound, C10H8INO2, is an N-substituted phthalimide derivative in which the crystallog... more The title compound, C10H8INO2, is an N-substituted phthalimide derivative in which the crystallographic intermolecular contact pattern consists of I� � �I, C—H� � �I, C—H� � �O and aromatic �–� interactions.
Acta Crystallographica Section E Structure Reports Online
The title compound, C27H47NO3, is a (3-hydroxypropyl)amide derivative of naturally occurring en... more The title compound, C27H47NO3, is a (3-hydroxypropyl)amide derivative of naturally occurring enantiopure lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid). The molecule contains four fused rings: three six-membered rings in chair conformations and one five-membered ring in a half-chair form. The two terminal six-membered rings are cis-fused, while other rings are trans-fused. The structure contains an intramolecular O—H⋯O hydrogen bond and a similar hydrogen-bond framework to the corresponding deoxycholic and chenodeoxycholic acid derivatives. Intermolecular O—H⋯O and N—H⋯O interactions are also present in the crystal. This compound seems to have at least two polymorphic forms from a comparison of the X-ray powder pattern simulated from the present structure of the title compound and that previously obtained for the powder sample.
1H and 13C NMR spectra of eleven 2-phenacylbenzoxazoles (ketimine form) show that their CDCl(3)-s... more 1H and 13C NMR spectra of eleven 2-phenacylbenzoxazoles (ketimine form) show that their CDCl(3)-solutions contains also (Z)-2-(benzo[d]oxazol-2-yl)-1-phenylethenols (enolimine form). Intramolecular hydrogen bonding in the latter tautomer was found to be significantly weaker than that one in respective (Z)-2-(2-hydroxy-2-phenylvinyl)pyridines. Integrals of the 1H NMR signals were used to evaluate the molar ratio of the tautomers. Strong electron-donating substituents were found to stabilize the ketimine tautomer. pK(T) (negative logarithm of the equilibrium constant, K(T) = [ketimine]/[enolimine]) was found to be linearly dependent on the Hammett substituent constant σ. The results of the MP2 ab initio calculations reveal enolimine including an intramolecular OH…N hydrogen bond to be the most stable form both with electron-donor and electron-acceptor substituents. The stability of ketimines is an intermediate of those found for enolimines and enaminones i.e., (E)-2-(benzo[d]oxazol-2(...
In this paper the title compound 3,5,4 0 -trihydroxy-6,7-dimethoxy-flavone (Eupalitin) has been i... more In this paper the title compound 3,5,4 0 -trihydroxy-6,7-dimethoxy-flavone (Eupalitin) has been isolated from Asparagus falcatus and characterized by UV, IR, NMR, mass spectra and X-ray single crystal diffraction. The 3,5,4 0 -trihydroxy-6,7-dimethoxy-flavone crystallizes in a monoclinic space group P2 1 /n with a = 6.2527(2), b = 17.2821(6), c = 13.5476(5) Å , b = 100.274(2)°and Z = 4, b = 100.274(2)°and V = 1440.48(9) Å 3 . The crystal structure are stabilized by intra-and intermolecular O-HÁÁÁO hydrogen bonds. Molecules pack into infinite zigzag-like layers with these hydrogen bonds.
Abstract In this paper the title compound 3,5,40-trihydroxy- 6,7-dimethoxy-flavone (Eupalitin) ha... more Abstract In this paper the title compound 3,5,40-trihydroxy- 6,7-dimethoxy-flavone (Eupalitin) has been isolated from Asparagus falcatus and characterized by UV, IR, NMR, mass spectra and X-ray single crystal diffraction. The 3,5,40-trihydroxy-6,7-dimethoxy-flavone crystallizes in a monoclinic space group P21/n with a = 6.2527(2), b = 17.2821(6), c = 13.5476(5)A ° , b = 100.274(2)� and Z = 4, b = 100.274(2)� and V = 1440.48(9) A ° 3. The crystal structure are stabilized by intra- and intermolecular O–H���O hydrogen bonds. Molecules pack into infinite zigzag-like layers with these hydrogen bonds.
ABSTRACT The binding of different categories of alkyl ammonium (secondary and tertiary mono- and ... more ABSTRACT The binding of different categories of alkyl ammonium (secondary and tertiary mono- and di-ammonium) salts by resorcinarenes and a pyrogallarene through weak interactions were analyzed in all phases. 1H NMR spectroscopy and electrospray ionisation mass spectrometry were utilized in analyzing the complexes in solution and in the gas phase respectively. The 1H NMR titration studies in methanol-d4 reveal the association constants for the 1:1 complexes to vary according to the electronic properties of hosts as well as the size, geometric orientation and charge concentration of the guest cations with binding constants of up to 950 M-1 in some cases. Mass spectrometry reveals 1:1 monomeric and 1:2 dimeric complexes in the gas phase. Six co-crystals, three of which are dimeric host-guest capsular assemblies, two open inclusion complexes and a pseudocapsular methanol solvate were analyzed in the solid state through single-crystal X-ray diffraction. The X-ray structures confirm the complexes to be held together by multiple cation···π, CH···π and hydrogen bond interactions.
ABSTRACT Five compounds bearing electron-deficient pentafluorophenyl as well as electron-rich (sa... more ABSTRACT Five compounds bearing electron-deficient pentafluorophenyl as well as electron-rich (salicylate or indole) aromatic moieties connected by amide or ester linkages were investigated by X-ray diffraction. In the crystals, various interactions (π–π, lone pair–π) between the different aromatic units are important structure controlling factors in addition to the stronger inter- or intramolecular hydrogen bonds induced by the amide and ester moieties. The hydrogen bonding leads to polymeric and macrocyclic assembly of the molecular building blocks.
A novel and improved room temperature synthesis of the monohydride catalyst trans-[RuCl(H)(dppe)2... more A novel and improved room temperature synthesis of the monohydride catalyst trans-[RuCl(H)(dppe)2] complex (1, dppe (1,2-bis(diphenylphosphino)ethane)=Ph2PCH2CH2PPh2) proceeds through oxidation of methanol (the solvent) by the pentacoordinated cis-[RuCl(dppe)2][PF6] complex and t-BuOK as the base is described. Compound 1 was fully characterized by NMR (1H, 13C, 31P), ESI-MS(TOF+), FTIR and elemental analysis. The X-ray structure of 1 was reported for the first time and unambiguously confirms the trans-configuration of the complex.
The amino acid L-phenylalanine has been cocrystallized with D-2-aminobutyric acid, C(9)H(11)NO(2)... more The amino acid L-phenylalanine has been cocrystallized with D-2-aminobutyric acid, C(9)H(11)NO(2).C(4)H(9)NO(2), D-norvaline, C(9)H(11)NO(2).C(5)H(11)NO(2), and D-methionine, C(9)H(11)NO(2).C(5)H(11)NO(2)S, with linear side chains, as well as with D-leucine, C(9)H(11)NO(2).C(6)H(13)NO(2), D-isoleucine, C(9)H(11)NO(2).C(6)H(13)NO(2), and D-allo-isoleucine, C(9)H(11)NO(2).C(6)H(13)NO(2), with branched side chains. The structures of these 1:1 complexes fall into two classes based on the observed hydrogen-bonding pattern. From a comparison with other L:D complexes involving hydrophobic amino acids and regular racemates, it is shown that the structure-directing properties of phenylalanine closely parallel those of valine and isoleucine but not those of leucine, which shares side-chain branching at C(gamma) with phenylalanine and is normally considered to be the most closely related non-aromatic amino acid.
Chemical communications (Cambridge, England), Jan 28, 2014
The syntheses and halogen bonded (XB) complexes of tetrahalogenated ethynyl cavitands are present... more The syntheses and halogen bonded (XB) complexes of tetrahalogenated ethynyl cavitands are presented. These cavitands act as quite rigid 3D multivalent halogen bond donors and show strong XB with oxygen, nitrogen and bromide XB acceptors.
The role of different anion geometries in anion–p interactions is discussed. The chemistry descri... more The role of different anion geometries in anion–p interactions is discussed. The chemistry described herein is different to the interaction of spherical cations with aromatics. The influence of different geometries makes selective anion recognition more complicated than respective cation sensing. The present structural study reveals attractive interactions between pentafluorophenyl units and geometrically diverse anions (linear, trigonal planar, tetrahedral and octahedral). Due to the electrostatic nature of anion–p interactions, the anion geometry seems to be irrelevant. The size of the anion controls the relative orientation of the anion and the p system (e.g. in compounds 1–3). The dimeric solid-state structure of ammonium tetrafluorophenolate betaine 4 shows p–p as well as anion–p interactions. In the solid-state structure of 5, the linear BrIBr anion is panelled by three pentafluorophenyl units.
N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and inter... more N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and intermolecular hydrogen bonds that leads to cavitand-like structures. Depending on the upper-rim substituents, self-inclusion was observed in solution and in the solid state. The self-inclusion can be disrupted at higher temperatures, whereas in the presence of small guests the self-included dimers spontaneously reorganize to 1:1 host-guest complexes. These host compounds show an interesting ability to bind a series of N-alkyl acetamide guests through intermolecular hydrogen bonds involving the carbonyl oxygen (C=O) atoms and the amide (NH) groups of the guests, the chloride anions (Cl(-)) and ammonium (NH2(+)) cations of the hosts, and also through CH⋅⋅⋅π interactions between the hosts and guests. The self-included and host-guest complexes were studied by single-crystal X-ray diffraction, NMR titration, and mass spectrometry.
ABSTRACT Addition of anions to perfluorinated 1,1′-biphenyl 1 or naphthalene 2 results in a shift... more ABSTRACT Addition of anions to perfluorinated 1,1′-biphenyl 1 or naphthalene 2 results in a shift of the 19F NMR signals. However, any specific interaction cannot be assigned to this effect. In order to study the interaction in more detail, the salt derivatives 3 and 4 were prepared and studied by single crystal X-ray diffraction revealing weak anion–π interactions in the solid state.
N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and inter... more N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and intermolecular hydrogen bonds that leads to cavitand-like structures. Depending on the upper-rim substituents, self-inclusion was observed in solution and in the solid state. The self-inclusion can be disrupted at higher temperatures, whereas in the presence of small guests the self-included dimers spontaneously reorganize to 1:1 host-guest complexes. These host compounds show an interesting ability to bind a series of N-alkyl acetamide guests through intermolecular hydrogen bonds involving the carbonyl oxygen (C=O) atoms and the amide (NH) groups of the guests, the chloride anions (Cl(-)) and ammonium (NH2(+)) cations of the hosts, and also through CH⋅⋅⋅π interactions between the hosts and guests. The self-included and host-guest complexes were studied by single-crystal X-ray diffraction, NMR titration, and mass spectrometry.
Single crystal X-ray structures (monoclinic space group P21) for methyl 3-oxo-5b-cholan-24-oate a... more Single crystal X-ray structures (monoclinic space group P21) for methyl 3-oxo-5b-cholan-24-oate and methyl 3,12-dioxo-5b-cholan-24-oate have been solved and compared with HF/6-31G* optimised structures. In the crystalline packings the side chains are connected with weak OC(sp3)H• • •O-type of interactions between C25–H and C24–O–C25 and the keto ends with weak C(sp3)H• • •O=C-type of interactions between C4–H and O=C3. The orientations of the side chains, which steric configurations are of great importance to the biological activity of the molecules, are compared with the experimental structure of methyl 3a-hydroxy-5b-cholan-24-oate. Probable reasons for the observed differences are discussed. In addition, 13C and 17O NMR chemical shifts of methyl 3-oxo-5b-cholan-24-oate and methyl 3,12-dioxo-5b-cholan-24-oate as well as the epimeric methyl 3a-hydroxy-5b-cholan-24-oate and methyl 3b-hydroxy-5b-cholan-24-oate have been calculated (DFT/B3LYP/6-311G*) and compared with the experimental...
The 1H and 13C NMR chemical shifts for six toxaphene congeners: 2-exo,3-endo,6-exo,8,9,10-hexachl... more The 1H and 13C NMR chemical shifts for six toxaphene congeners: 2-exo,3-endo,6-exo,8,9,10-hexachloro- (1), 2-exo,3-endo,5-exo,9,9,10, 10-heptachloro- (2), 2-exo,3-endo,6-exo,8,9,10,10-heptachloro- (3), 2-exo,3-endo,5-exo,6-endo,8,9,10-heptachloro- (4), 2-exo,3-endo,5-exo, 6-endo,8,9,9,10-octachlorobornane (5) and 2,5-endo,6-exo,8,9,9,10,10-octachloro-2-bornene (6) are reported. Their chemical shift assignments have been obtained by means of Pulsed Field Gradient (PFG) Double Quantum Filtered (DQF) 1H,1H correlation spectroscopy (COSY), PFG 1H,13C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG 1H,13C Heteronuclear Multiple Bond Correlation (HMBC) experiments. A single crystal X-ray structural analysis was made for compounds 1, 3, 4 and 6. The prevalences of two octachlorobornene rotamers (6a,6b) were elucidated by ab initio MO method and single point DFT/GIAO calculations for 13C chemical shifts. Theoretical calculations proved that the single crystal structure of 6 correspo...
Acta Crystallographica Section E Structure Reports Online
The title compound, C(33)H(3)F(20)N(3)O(4), is a highly fluorinated organic imide that was isolat... more The title compound, C(33)H(3)F(20)N(3)O(4), is a highly fluorinated organic imide that was isolated as an unexpected product from the reaction of 2,6-diamino-pyridine with 2,3,4,5,6-penta-fluoro-benzoyl chloride in a 1:2 molar ratio. The mol-ecule is located on a twofold axis and one of its symmetry-independent 2,3,4,5,6-penta-fluoro-benzoyl groups is disordered over two sets of sites, the occupancy of the major component being 0.773 (3). In the major component, the dihedral angle between the perfluoro-phenyl groups is 63.64 (10)°, and these groups form dihedral angles of 67.14 (7) and 21.1 (2)° with the pyridine core. Short inter-molecular C-H⋯O and C-H⋯N contacts are found in the crystal structure.
Acta Crystallographica Section E Structure Reports Online
The title compound, C10H8INO2, is an N-substituted phthalimide derivative in which the crystallog... more The title compound, C10H8INO2, is an N-substituted phthalimide derivative in which the crystallographic intermolecular contact pattern consists of I� � �I, C—H� � �I, C—H� � �O and aromatic �–� interactions.
Acta Crystallographica Section E Structure Reports Online
The title compound, C27H47NO3, is a (3-hydroxypropyl)amide derivative of naturally occurring en... more The title compound, C27H47NO3, is a (3-hydroxypropyl)amide derivative of naturally occurring enantiopure lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid). The molecule contains four fused rings: three six-membered rings in chair conformations and one five-membered ring in a half-chair form. The two terminal six-membered rings are cis-fused, while other rings are trans-fused. The structure contains an intramolecular O—H⋯O hydrogen bond and a similar hydrogen-bond framework to the corresponding deoxycholic and chenodeoxycholic acid derivatives. Intermolecular O—H⋯O and N—H⋯O interactions are also present in the crystal. This compound seems to have at least two polymorphic forms from a comparison of the X-ray powder pattern simulated from the present structure of the title compound and that previously obtained for the powder sample.
1H and 13C NMR spectra of eleven 2-phenacylbenzoxazoles (ketimine form) show that their CDCl(3)-s... more 1H and 13C NMR spectra of eleven 2-phenacylbenzoxazoles (ketimine form) show that their CDCl(3)-solutions contains also (Z)-2-(benzo[d]oxazol-2-yl)-1-phenylethenols (enolimine form). Intramolecular hydrogen bonding in the latter tautomer was found to be significantly weaker than that one in respective (Z)-2-(2-hydroxy-2-phenylvinyl)pyridines. Integrals of the 1H NMR signals were used to evaluate the molar ratio of the tautomers. Strong electron-donating substituents were found to stabilize the ketimine tautomer. pK(T) (negative logarithm of the equilibrium constant, K(T) = [ketimine]/[enolimine]) was found to be linearly dependent on the Hammett substituent constant σ. The results of the MP2 ab initio calculations reveal enolimine including an intramolecular OH…N hydrogen bond to be the most stable form both with electron-donor and electron-acceptor substituents. The stability of ketimines is an intermediate of those found for enolimines and enaminones i.e., (E)-2-(benzo[d]oxazol-2(...
In this paper the title compound 3,5,4 0 -trihydroxy-6,7-dimethoxy-flavone (Eupalitin) has been i... more In this paper the title compound 3,5,4 0 -trihydroxy-6,7-dimethoxy-flavone (Eupalitin) has been isolated from Asparagus falcatus and characterized by UV, IR, NMR, mass spectra and X-ray single crystal diffraction. The 3,5,4 0 -trihydroxy-6,7-dimethoxy-flavone crystallizes in a monoclinic space group P2 1 /n with a = 6.2527(2), b = 17.2821(6), c = 13.5476(5) Å , b = 100.274(2)°and Z = 4, b = 100.274(2)°and V = 1440.48(9) Å 3 . The crystal structure are stabilized by intra-and intermolecular O-HÁÁÁO hydrogen bonds. Molecules pack into infinite zigzag-like layers with these hydrogen bonds.
Abstract In this paper the title compound 3,5,40-trihydroxy- 6,7-dimethoxy-flavone (Eupalitin) ha... more Abstract In this paper the title compound 3,5,40-trihydroxy- 6,7-dimethoxy-flavone (Eupalitin) has been isolated from Asparagus falcatus and characterized by UV, IR, NMR, mass spectra and X-ray single crystal diffraction. The 3,5,40-trihydroxy-6,7-dimethoxy-flavone crystallizes in a monoclinic space group P21/n with a = 6.2527(2), b = 17.2821(6), c = 13.5476(5)A ° , b = 100.274(2)� and Z = 4, b = 100.274(2)� and V = 1440.48(9) A ° 3. The crystal structure are stabilized by intra- and intermolecular O–H���O hydrogen bonds. Molecules pack into infinite zigzag-like layers with these hydrogen bonds.
ABSTRACT The binding of different categories of alkyl ammonium (secondary and tertiary mono- and ... more ABSTRACT The binding of different categories of alkyl ammonium (secondary and tertiary mono- and di-ammonium) salts by resorcinarenes and a pyrogallarene through weak interactions were analyzed in all phases. 1H NMR spectroscopy and electrospray ionisation mass spectrometry were utilized in analyzing the complexes in solution and in the gas phase respectively. The 1H NMR titration studies in methanol-d4 reveal the association constants for the 1:1 complexes to vary according to the electronic properties of hosts as well as the size, geometric orientation and charge concentration of the guest cations with binding constants of up to 950 M-1 in some cases. Mass spectrometry reveals 1:1 monomeric and 1:2 dimeric complexes in the gas phase. Six co-crystals, three of which are dimeric host-guest capsular assemblies, two open inclusion complexes and a pseudocapsular methanol solvate were analyzed in the solid state through single-crystal X-ray diffraction. The X-ray structures confirm the complexes to be held together by multiple cation···π, CH···π and hydrogen bond interactions.
ABSTRACT Five compounds bearing electron-deficient pentafluorophenyl as well as electron-rich (sa... more ABSTRACT Five compounds bearing electron-deficient pentafluorophenyl as well as electron-rich (salicylate or indole) aromatic moieties connected by amide or ester linkages were investigated by X-ray diffraction. In the crystals, various interactions (π–π, lone pair–π) between the different aromatic units are important structure controlling factors in addition to the stronger inter- or intramolecular hydrogen bonds induced by the amide and ester moieties. The hydrogen bonding leads to polymeric and macrocyclic assembly of the molecular building blocks.
A novel and improved room temperature synthesis of the monohydride catalyst trans-[RuCl(H)(dppe)2... more A novel and improved room temperature synthesis of the monohydride catalyst trans-[RuCl(H)(dppe)2] complex (1, dppe (1,2-bis(diphenylphosphino)ethane)=Ph2PCH2CH2PPh2) proceeds through oxidation of methanol (the solvent) by the pentacoordinated cis-[RuCl(dppe)2][PF6] complex and t-BuOK as the base is described. Compound 1 was fully characterized by NMR (1H, 13C, 31P), ESI-MS(TOF+), FTIR and elemental analysis. The X-ray structure of 1 was reported for the first time and unambiguously confirms the trans-configuration of the complex.
The amino acid L-phenylalanine has been cocrystallized with D-2-aminobutyric acid, C(9)H(11)NO(2)... more The amino acid L-phenylalanine has been cocrystallized with D-2-aminobutyric acid, C(9)H(11)NO(2).C(4)H(9)NO(2), D-norvaline, C(9)H(11)NO(2).C(5)H(11)NO(2), and D-methionine, C(9)H(11)NO(2).C(5)H(11)NO(2)S, with linear side chains, as well as with D-leucine, C(9)H(11)NO(2).C(6)H(13)NO(2), D-isoleucine, C(9)H(11)NO(2).C(6)H(13)NO(2), and D-allo-isoleucine, C(9)H(11)NO(2).C(6)H(13)NO(2), with branched side chains. The structures of these 1:1 complexes fall into two classes based on the observed hydrogen-bonding pattern. From a comparison with other L:D complexes involving hydrophobic amino acids and regular racemates, it is shown that the structure-directing properties of phenylalanine closely parallel those of valine and isoleucine but not those of leucine, which shares side-chain branching at C(gamma) with phenylalanine and is normally considered to be the most closely related non-aromatic amino acid.
Chemical communications (Cambridge, England), Jan 28, 2014
The syntheses and halogen bonded (XB) complexes of tetrahalogenated ethynyl cavitands are present... more The syntheses and halogen bonded (XB) complexes of tetrahalogenated ethynyl cavitands are presented. These cavitands act as quite rigid 3D multivalent halogen bond donors and show strong XB with oxygen, nitrogen and bromide XB acceptors.
The role of different anion geometries in anion–p interactions is discussed. The chemistry descri... more The role of different anion geometries in anion–p interactions is discussed. The chemistry described herein is different to the interaction of spherical cations with aromatics. The influence of different geometries makes selective anion recognition more complicated than respective cation sensing. The present structural study reveals attractive interactions between pentafluorophenyl units and geometrically diverse anions (linear, trigonal planar, tetrahedral and octahedral). Due to the electrostatic nature of anion–p interactions, the anion geometry seems to be irrelevant. The size of the anion controls the relative orientation of the anion and the p system (e.g. in compounds 1–3). The dimeric solid-state structure of ammonium tetrafluorophenolate betaine 4 shows p–p as well as anion–p interactions. In the solid-state structure of 5, the linear BrIBr anion is panelled by three pentafluorophenyl units.
N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and inter... more N-alkyl ammonium resorcinarene chlorides are stabilized by an intricate array of intra- and intermolecular hydrogen bonds that leads to cavitand-like structures. Depending on the upper-rim substituents, self-inclusion was observed in solution and in the solid state. The self-inclusion can be disrupted at higher temperatures, whereas in the presence of small guests the self-included dimers spontaneously reorganize to 1:1 host-guest complexes. These host compounds show an interesting ability to bind a series of N-alkyl acetamide guests through intermolecular hydrogen bonds involving the carbonyl oxygen (C=O) atoms and the amide (NH) groups of the guests, the chloride anions (Cl(-)) and ammonium (NH2(+)) cations of the hosts, and also through CH⋅⋅⋅π interactions between the hosts and guests. The self-included and host-guest complexes were studied by single-crystal X-ray diffraction, NMR titration, and mass spectrometry.
ABSTRACT Addition of anions to perfluorinated 1,1′-biphenyl 1 or naphthalene 2 results in a shift... more ABSTRACT Addition of anions to perfluorinated 1,1′-biphenyl 1 or naphthalene 2 results in a shift of the 19F NMR signals. However, any specific interaction cannot be assigned to this effect. In order to study the interaction in more detail, the salt derivatives 3 and 4 were prepared and studied by single crystal X-ray diffraction revealing weak anion–π interactions in the solid state.
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Papers by Arto Valkonen