A series of phosphonium salts with pentafluorobenzyl substituents have been synthesized and were ... more A series of phosphonium salts with pentafluorobenzyl substituents have been synthesized and were investigated in the crystal as well as in solution. The solid state structures of 1a, 1b and 2d reveal the presence of anion-π as well as CH-anion interactions. The two attractive, yet competitive forces seem to act in concert and a directing effect of the CH interaction on the relative position between anion and π-system is observed. The search for anion-π interactions in solution failed. Only CH-anion interactions proved to be important in solution.
The directionality of interaction of electron-deficient π systems with spherical anions (e.g,. ha... more The directionality of interaction of electron-deficient π systems with spherical anions (e.g,. halides) can be controlled by secondary effects like NH or CH hydrogen bonding. In this study a series of pentafluorophenyl-substituted salts with polyhalide anions is investigated. The compounds are obtained by aerobic oxidation of the corresponding halide upon crystallization. Solid-state structures reveal that in bromide 2, directing NH-anion interactions position the bromide ion in an η(1)-type fashion over but not in the center of the aromatic ring. The same directing forces are effective in corresponding tribromide salt 3. In the crystal, the bromide ion is paneled by four electron-deficient aromatic ring systems. In addition, compounds 4 and 6, which have triiodide and the rare tetraiodide dianion as anions, are described. Computational studies reveal that the latter is highly unstable. In the present case it is stabilized by the crystal lattice, for example, by interaction with electron-deficient π systems.
Eight single crystal X-ray structures, solid-state NMR spectroscopic, and theoretical studies uti... more Eight single crystal X-ray structures, solid-state NMR spectroscopic, and theoretical studies utilizing QTAIM methodology were used to characterize the 2-acyl (alkyl in acyl = methyl, ethyl, t-butyl, and 1- adamantyl) amino-6-R-pyridine/4-R0-benzoic acid (R,R0 = H or Me) cocrystals. As expected among alkyl groups 1-adamantyl due to its bulkiness has the most significant effect on the relative positions of molecules in cocrystals. In addition, the subtle electronic and steric effects by the methyl substituents were observed. The theoretical calculations with full geometry optimizations are in agreement with the experimental findings (geometry, energy of hydrogen bonds). Based on the crystal structures and calculations it is concluded that p-methyl substituent in benzoic acid increase the hydrogen bond accepting ability of the C@O oxygen and decreases the hydrogen bond donating ability of OH proton. The 15N solid-state (CP MAS) NMR chemical shifts prove that molecules in cocrystal are held together by hydrogen bonding. The biggest variation in the 15N chemical shift of acylamino nitrogen can be related with the size of the alkyl group in acyl moiety.
Aggregation of 2-acylaminopyridines and their 6-methyl derivatives in chloroform solution was stu... more Aggregation of 2-acylaminopyridines and their 6-methyl derivatives in chloroform solution was studied by 1 H, 13 C, and 15 N NMR spectroscopies. The results were compared with 13 C and 15 N CPMAS NMR and IR spectral as well as with X-ray structural data. Intermolecular interactions in solution and in solid state were found to have a similar nature. Relatively strong N amide-H · · · N pyridine intermolecular hydrogen bonds enable dimerization to take place. Steric interactions in N-pivaloyl-and N-1-adamantylcarbonyl as well as that caused by the 6-methyl group hinder formation of the dimeric aggregates stabilized by the N amide-H · · · N pyridine intermolecular hydrogen bonds. In general, the DFT optimized geometries of the aggregates in chloroform solution are in agreement with the X-ray crystal structures. Wavenumbers of the stretching vibration band of the CdO group were also found indicative of the type of hydrogen bond present in the solid state.
Angewandte Chemie International Edition in English, 1996
... Pluladclphio. PA. 1976. p. 649. A Double Calixl4larene in a 1,3-altevnate Conformation** Jose... more ... Pluladclphio. PA. 1976. p. 649. A Double Calixl4larene in a 1,3-altevnate Conformation** Jose-Antonio Perez-Adelmar, Herve Abraham, Concha Srinchez, Kari Rissanen, Pilar Prados,* and Javier de Mendoza* ... c) Top view along the u-axis, showing the internal diameter of 8. ...
A simple 18-crown-6-based bis-urea receptor R(1) was synthesized in three steps from a commercial... more A simple 18-crown-6-based bis-urea receptor R(1) was synthesized in three steps from a commercial starting material. The receptor's behavior toward anions, cations, and ion pairs was studied in solution with (1)H NMR, in solid state with single-crystal X-ray diffraction, and in gas phase with mass spectrometry. In 4:1 CDCl3/dimethyl sulfoxide solution the receptor's binding preference of halide anions is I(-) < Br(-) < Cl(-) following the trend of the hydrogen-bonding acceptor ability of the anions. The receptor shows a remarkable positive cooperativity toward halide anions Cl(-), Br(-), and I(-) when complexed with Na(+), K(+), or Rb(+). The solid-state binding modes of R(1) with alkali and ammonium halides or oxyanions were confirmed by the X-ray structures of R(1) with KF, KCl, KBr, KI, RbCl, NH4Cl, NH4Br, KAcO, K2CO3, and K2SO4. They clearly present two different binding modes, either as separated or contact ion pairs depending on the nature and size of the bound c...
A novel modular approach to electron-deficient and electron-rich M6L4 cages is presented. From th... more A novel modular approach to electron-deficient and electron-rich M6L4 cages is presented. From the same starting compound, via a minor modulation of the synthesis route, two C3-symmetric ligands L1 and L2 with different electronic properties are obtained in good yield. The trifluoro-triethynylbenzene-based ligand L1 is more electron-deficient than the well-known 2,4,6-tri(4-pyridyl)-1,3,5-triazine, while the trimethoxy-triethynylbenzene-based ligand L2 is more electron-rich than the corresponding benzene analogue. Complexation of the ligands with cis-protected square-planar [(dppp)Pt(OTf)2] or [(dppp)Pd(OTf)2] corner-complexes yields two electron-deficient (1a and 1b) and two electron-rich (2a and 2b) M6L4 cages. The single crystal X-ray diffraction study of 1a and 2a confirms the expected octahedral shape with a ca. 2000 Å(3) cavity and ca. 11 Å wide apertures. The crystallographically determined diameters of 1a and 2a are 3.7 and 3.6 nm, respectively. The hydrodynamic diameters obtained from the DOSY NMR in CDCl3:CD3OD (4:1), and diameters calculated from collision cross sections (CCS) acquired by ion-mobility mass spectrometry (IM-MS) were for all four cages similar. In solution, the cage structures have diameters between 3.3 to 3.6 nm, while in the gas phase the corresponding diameters varied between 3.4 to 3.6 nm. In addition to the structural information the relative stabilities of the Pt6L4 and Pd6L4 cages were studied in the gas phase by collision-induced dissociation (CID) experiments, and the photophysical properties of the ligands L1 and L2 and cages 1a, 1b, 2a, and 2b were studied by UV-vis and fluorescence spectroscopy.
Journal of the American Chemical Society, Jan 25, 2015
We report (129)Xe NMR experiments showing that a Fe4L6 metallosupramolecular cage can encapsulate... more We report (129)Xe NMR experiments showing that a Fe4L6 metallosupramolecular cage can encapsulate xenon in water with a binding constant of 16 M(-1). The observations pave the way for exploiting metallosupramolecular cages as economical means to extract rare gases as well as (129)Xe NMR-based bio-, pH, and temperature sensors. Xe in the Fe4L6 cage has an unusual chemical shift downfield from free Xe in water. The exchange rate between the encapsulated and free Xe was determined to be about 10 Hz, potentially allowing signal amplification via chemical exchange saturation transfer. Computational treatment showed that dynamical effects of Xe motion as well as relativistic effects have significant contributions to the chemical shift of Xe in the cage and enabled the replication of the observed linear temperature dependence of the shift.
The title compound,[Ru (N3) 2 (C25H22P2) 2] or cis-[Ru (N3) 2 (dppm) 2][dppm is bis (diphenylphos... more The title compound,[Ru (N3) 2 (C25H22P2) 2] or cis-[Ru (N3) 2 (dppm) 2][dppm is bis (diphenylphosphino) methane], was obtained unexpectedly from our attempts to prepare new ruthenium molecular wires using organic bridging ligands. Both the azido ligands ...
2,5-Diethoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene, C(20)H(30)O(2)Si(2), (I), constitutes one o... more 2,5-Diethoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene, C(20)H(30)O(2)Si(2), (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5-dialkoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene derivatives, used in the preparation of oligo(phenyleneethynylene)s via Pd/Cu-catalysed cross-coupling. 2,5-Diethoxy-1,4-diethynylbenzene, C(14)H(14)O(2), (II), results from protodesilylation of (I). 1,4-Diethynyl-2,5-bis(heptyloxy)benzene, C(24)H(34)O(2), (III), is a long alkyloxy chain analogue of (II). The molecules of compounds (I)-(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and intermolecular interactions of adjacent molecules. All the compounds exhibit weak intermolecular interactions that are only slightly shorter than the sum of the van der Waals radii of the interacting atoms. Compound (I) displays C-H...pi inter...
ABSTRACT The synthesis strategy for the preparation of novel platinum acetylide homometallic and ... more ABSTRACT The synthesis strategy for the preparation of novel platinum acetylide homometallic and heterobimetallic dendrimers (containing Fe as the other metal fragment) based on a 2,4,6-tris(4-ethynyl)phenyl-1,3,5-triazine core (3) is reported. All the dendrimer generations (G0-G2) were synthesized under copper-free conditions following a divergent route. The G0-Pt dendrimer (4) was synthesized using the 1,3,5-triazine core (3) and cis-[Pt(PEt3)(2)Cl-2] with a molar ratio of 1/4. The advantage of the current method is that different dendrimers can be prepared by following the same procedure with only changes in the molar ratios of the reactants involved. For instance, when 3 reacts with 4 in a 4/1 molar ratio, the G1 dendrimer 7 is afforded without the peripheral Pt moiety, but the G1 dendrimer with the peripheral Pt moiety (8) is formed when 3 reacts with 4 in a 1/3 molar ratio. On the other hand, the G2 dendrimer with a peripheral Pt moiety (9) is synthesized when 7 reacts with 4 in a 1/6 molar ratio. The heterobimetallic dendrimers were synthesized up to generation 1 by capping the corresponding Pt dendrimers with the ethynylferrocenyl group (EFC). The respective G0 (6)- and G1-capped (10) dendrimers were synthesized when EFC reacted with 4 and 8 in molar ratios of 9/1 and 18/1, respectively. Nonlinear optical (NLO) polarizabilities measured by hyper-Rayleigh scattering (HRS) have been evaluated for the core 3, for the GO dendrimer 4, and for the GO dendrimer capped with EFC (6). In spite of the fact that the stability of the higher generations in chloroform is too low to allow HRS measurements, the reported NLO results show a remarkable enhancement (plus 50%) upon capping the zero dendrimer generation (6), reflecting the importance of the introduction of electron donor organometallic capping groups in the hyperpolarizabilities of the resulting dendrimers.
A series of phosphonium salts with pentafluorobenzyl substituents have been synthesized and were ... more A series of phosphonium salts with pentafluorobenzyl substituents have been synthesized and were investigated in the crystal as well as in solution. The solid state structures of 1a, 1b and 2d reveal the presence of anion-π as well as CH-anion interactions. The two attractive, yet competitive forces seem to act in concert and a directing effect of the CH interaction on the relative position between anion and π-system is observed. The search for anion-π interactions in solution failed. Only CH-anion interactions proved to be important in solution.
The directionality of interaction of electron-deficient π systems with spherical anions (e.g,. ha... more The directionality of interaction of electron-deficient π systems with spherical anions (e.g,. halides) can be controlled by secondary effects like NH or CH hydrogen bonding. In this study a series of pentafluorophenyl-substituted salts with polyhalide anions is investigated. The compounds are obtained by aerobic oxidation of the corresponding halide upon crystallization. Solid-state structures reveal that in bromide 2, directing NH-anion interactions position the bromide ion in an η(1)-type fashion over but not in the center of the aromatic ring. The same directing forces are effective in corresponding tribromide salt 3. In the crystal, the bromide ion is paneled by four electron-deficient aromatic ring systems. In addition, compounds 4 and 6, which have triiodide and the rare tetraiodide dianion as anions, are described. Computational studies reveal that the latter is highly unstable. In the present case it is stabilized by the crystal lattice, for example, by interaction with electron-deficient π systems.
Eight single crystal X-ray structures, solid-state NMR spectroscopic, and theoretical studies uti... more Eight single crystal X-ray structures, solid-state NMR spectroscopic, and theoretical studies utilizing QTAIM methodology were used to characterize the 2-acyl (alkyl in acyl = methyl, ethyl, t-butyl, and 1- adamantyl) amino-6-R-pyridine/4-R0-benzoic acid (R,R0 = H or Me) cocrystals. As expected among alkyl groups 1-adamantyl due to its bulkiness has the most significant effect on the relative positions of molecules in cocrystals. In addition, the subtle electronic and steric effects by the methyl substituents were observed. The theoretical calculations with full geometry optimizations are in agreement with the experimental findings (geometry, energy of hydrogen bonds). Based on the crystal structures and calculations it is concluded that p-methyl substituent in benzoic acid increase the hydrogen bond accepting ability of the C@O oxygen and decreases the hydrogen bond donating ability of OH proton. The 15N solid-state (CP MAS) NMR chemical shifts prove that molecules in cocrystal are held together by hydrogen bonding. The biggest variation in the 15N chemical shift of acylamino nitrogen can be related with the size of the alkyl group in acyl moiety.
Aggregation of 2-acylaminopyridines and their 6-methyl derivatives in chloroform solution was stu... more Aggregation of 2-acylaminopyridines and their 6-methyl derivatives in chloroform solution was studied by 1 H, 13 C, and 15 N NMR spectroscopies. The results were compared with 13 C and 15 N CPMAS NMR and IR spectral as well as with X-ray structural data. Intermolecular interactions in solution and in solid state were found to have a similar nature. Relatively strong N amide-H · · · N pyridine intermolecular hydrogen bonds enable dimerization to take place. Steric interactions in N-pivaloyl-and N-1-adamantylcarbonyl as well as that caused by the 6-methyl group hinder formation of the dimeric aggregates stabilized by the N amide-H · · · N pyridine intermolecular hydrogen bonds. In general, the DFT optimized geometries of the aggregates in chloroform solution are in agreement with the X-ray crystal structures. Wavenumbers of the stretching vibration band of the CdO group were also found indicative of the type of hydrogen bond present in the solid state.
Angewandte Chemie International Edition in English, 1996
... Pluladclphio. PA. 1976. p. 649. A Double Calixl4larene in a 1,3-altevnate Conformation** Jose... more ... Pluladclphio. PA. 1976. p. 649. A Double Calixl4larene in a 1,3-altevnate Conformation** Jose-Antonio Perez-Adelmar, Herve Abraham, Concha Srinchez, Kari Rissanen, Pilar Prados,* and Javier de Mendoza* ... c) Top view along the u-axis, showing the internal diameter of 8. ...
A simple 18-crown-6-based bis-urea receptor R(1) was synthesized in three steps from a commercial... more A simple 18-crown-6-based bis-urea receptor R(1) was synthesized in three steps from a commercial starting material. The receptor's behavior toward anions, cations, and ion pairs was studied in solution with (1)H NMR, in solid state with single-crystal X-ray diffraction, and in gas phase with mass spectrometry. In 4:1 CDCl3/dimethyl sulfoxide solution the receptor's binding preference of halide anions is I(-) < Br(-) < Cl(-) following the trend of the hydrogen-bonding acceptor ability of the anions. The receptor shows a remarkable positive cooperativity toward halide anions Cl(-), Br(-), and I(-) when complexed with Na(+), K(+), or Rb(+). The solid-state binding modes of R(1) with alkali and ammonium halides or oxyanions were confirmed by the X-ray structures of R(1) with KF, KCl, KBr, KI, RbCl, NH4Cl, NH4Br, KAcO, K2CO3, and K2SO4. They clearly present two different binding modes, either as separated or contact ion pairs depending on the nature and size of the bound c...
A novel modular approach to electron-deficient and electron-rich M6L4 cages is presented. From th... more A novel modular approach to electron-deficient and electron-rich M6L4 cages is presented. From the same starting compound, via a minor modulation of the synthesis route, two C3-symmetric ligands L1 and L2 with different electronic properties are obtained in good yield. The trifluoro-triethynylbenzene-based ligand L1 is more electron-deficient than the well-known 2,4,6-tri(4-pyridyl)-1,3,5-triazine, while the trimethoxy-triethynylbenzene-based ligand L2 is more electron-rich than the corresponding benzene analogue. Complexation of the ligands with cis-protected square-planar [(dppp)Pt(OTf)2] or [(dppp)Pd(OTf)2] corner-complexes yields two electron-deficient (1a and 1b) and two electron-rich (2a and 2b) M6L4 cages. The single crystal X-ray diffraction study of 1a and 2a confirms the expected octahedral shape with a ca. 2000 Å(3) cavity and ca. 11 Å wide apertures. The crystallographically determined diameters of 1a and 2a are 3.7 and 3.6 nm, respectively. The hydrodynamic diameters obtained from the DOSY NMR in CDCl3:CD3OD (4:1), and diameters calculated from collision cross sections (CCS) acquired by ion-mobility mass spectrometry (IM-MS) were for all four cages similar. In solution, the cage structures have diameters between 3.3 to 3.6 nm, while in the gas phase the corresponding diameters varied between 3.4 to 3.6 nm. In addition to the structural information the relative stabilities of the Pt6L4 and Pd6L4 cages were studied in the gas phase by collision-induced dissociation (CID) experiments, and the photophysical properties of the ligands L1 and L2 and cages 1a, 1b, 2a, and 2b were studied by UV-vis and fluorescence spectroscopy.
Journal of the American Chemical Society, Jan 25, 2015
We report (129)Xe NMR experiments showing that a Fe4L6 metallosupramolecular cage can encapsulate... more We report (129)Xe NMR experiments showing that a Fe4L6 metallosupramolecular cage can encapsulate xenon in water with a binding constant of 16 M(-1). The observations pave the way for exploiting metallosupramolecular cages as economical means to extract rare gases as well as (129)Xe NMR-based bio-, pH, and temperature sensors. Xe in the Fe4L6 cage has an unusual chemical shift downfield from free Xe in water. The exchange rate between the encapsulated and free Xe was determined to be about 10 Hz, potentially allowing signal amplification via chemical exchange saturation transfer. Computational treatment showed that dynamical effects of Xe motion as well as relativistic effects have significant contributions to the chemical shift of Xe in the cage and enabled the replication of the observed linear temperature dependence of the shift.
The title compound,[Ru (N3) 2 (C25H22P2) 2] or cis-[Ru (N3) 2 (dppm) 2][dppm is bis (diphenylphos... more The title compound,[Ru (N3) 2 (C25H22P2) 2] or cis-[Ru (N3) 2 (dppm) 2][dppm is bis (diphenylphosphino) methane], was obtained unexpectedly from our attempts to prepare new ruthenium molecular wires using organic bridging ligands. Both the azido ligands ...
2,5-Diethoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene, C(20)H(30)O(2)Si(2), (I), constitutes one o... more 2,5-Diethoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene, C(20)H(30)O(2)Si(2), (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5-dialkoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene derivatives, used in the preparation of oligo(phenyleneethynylene)s via Pd/Cu-catalysed cross-coupling. 2,5-Diethoxy-1,4-diethynylbenzene, C(14)H(14)O(2), (II), results from protodesilylation of (I). 1,4-Diethynyl-2,5-bis(heptyloxy)benzene, C(24)H(34)O(2), (III), is a long alkyloxy chain analogue of (II). The molecules of compounds (I)-(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and intermolecular interactions of adjacent molecules. All the compounds exhibit weak intermolecular interactions that are only slightly shorter than the sum of the van der Waals radii of the interacting atoms. Compound (I) displays C-H...pi inter...
ABSTRACT The synthesis strategy for the preparation of novel platinum acetylide homometallic and ... more ABSTRACT The synthesis strategy for the preparation of novel platinum acetylide homometallic and heterobimetallic dendrimers (containing Fe as the other metal fragment) based on a 2,4,6-tris(4-ethynyl)phenyl-1,3,5-triazine core (3) is reported. All the dendrimer generations (G0-G2) were synthesized under copper-free conditions following a divergent route. The G0-Pt dendrimer (4) was synthesized using the 1,3,5-triazine core (3) and cis-[Pt(PEt3)(2)Cl-2] with a molar ratio of 1/4. The advantage of the current method is that different dendrimers can be prepared by following the same procedure with only changes in the molar ratios of the reactants involved. For instance, when 3 reacts with 4 in a 4/1 molar ratio, the G1 dendrimer 7 is afforded without the peripheral Pt moiety, but the G1 dendrimer with the peripheral Pt moiety (8) is formed when 3 reacts with 4 in a 1/3 molar ratio. On the other hand, the G2 dendrimer with a peripheral Pt moiety (9) is synthesized when 7 reacts with 4 in a 1/6 molar ratio. The heterobimetallic dendrimers were synthesized up to generation 1 by capping the corresponding Pt dendrimers with the ethynylferrocenyl group (EFC). The respective G0 (6)- and G1-capped (10) dendrimers were synthesized when EFC reacted with 4 and 8 in molar ratios of 9/1 and 18/1, respectively. Nonlinear optical (NLO) polarizabilities measured by hyper-Rayleigh scattering (HRS) have been evaluated for the core 3, for the GO dendrimer 4, and for the GO dendrimer capped with EFC (6). In spite of the fact that the stability of the higher generations in chloroform is too low to allow HRS measurements, the reported NLO results show a remarkable enhancement (plus 50%) upon capping the zero dendrimer generation (6), reflecting the importance of the introduction of electron donor organometallic capping groups in the hyperpolarizabilities of the resulting dendrimers.
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QTAIM methodology were used to characterize the 2-acyl (alkyl in acyl = methyl, ethyl, t-butyl, and 1-
adamantyl) amino-6-R-pyridine/4-R0-benzoic acid (R,R0 = H or Me) cocrystals. As expected among alkyl
groups 1-adamantyl due to its bulkiness has the most significant effect on the relative positions of molecules
in cocrystals. In addition, the subtle electronic and steric effects by the methyl substituents were
observed. The theoretical calculations with full geometry optimizations are in agreement with the experimental
findings (geometry, energy of hydrogen bonds). Based on the crystal structures and calculations
it is concluded that p-methyl substituent in benzoic acid increase the hydrogen bond accepting ability of
the C@O oxygen and decreases the hydrogen bond donating ability of OH proton. The 15N solid-state (CP
MAS) NMR chemical shifts prove that molecules in cocrystal are held together by hydrogen bonding. The
biggest variation in the 15N chemical shift of acylamino nitrogen can be related with the size of the alkyl
group in acyl moiety.
QTAIM methodology were used to characterize the 2-acyl (alkyl in acyl = methyl, ethyl, t-butyl, and 1-
adamantyl) amino-6-R-pyridine/4-R0-benzoic acid (R,R0 = H or Me) cocrystals. As expected among alkyl
groups 1-adamantyl due to its bulkiness has the most significant effect on the relative positions of molecules
in cocrystals. In addition, the subtle electronic and steric effects by the methyl substituents were
observed. The theoretical calculations with full geometry optimizations are in agreement with the experimental
findings (geometry, energy of hydrogen bonds). Based on the crystal structures and calculations
it is concluded that p-methyl substituent in benzoic acid increase the hydrogen bond accepting ability of
the C@O oxygen and decreases the hydrogen bond donating ability of OH proton. The 15N solid-state (CP
MAS) NMR chemical shifts prove that molecules in cocrystal are held together by hydrogen bonding. The
biggest variation in the 15N chemical shift of acylamino nitrogen can be related with the size of the alkyl
group in acyl moiety.