Showing papers on "Pi interaction published in 2015"
TL;DR: The donor/acceptor role of the ring in the complexes is analyzed using the natural bond orbital computational tool, showing a remarkable contribution of orbital interactions to the global stabilization of the aerogen-π complexes.
Abstract: In this study, several lone pair-π and aerogen-π complexes between XeO3 and XeF4 and aromatic rings with different electronic natures (benzene, trifluorobenzene, and hexafluorobenzene) are optimized at the RI-MP2/aug-cc-pVTZ level of theory. All complexes are characterized as true minima by frequency analysis calculations. The donor/acceptor role of the ring in the complexes is analyzed using the natural bond orbital computational tool, showing a remarkable contribution of orbital interactions to the global stabilization of the aerogen-π complexes. Finally, Bader's AIM analysis of several complexes is performed to further characterize the lone pair-π and aerogen-π interactions.
59 citations
TL;DR: This perspective discusses reduced carbocyclic and acyclic π ligands; in certain categories, when no example of a rare-earth metal complex is available, a closely related actinide analogue is discussed.
Abstract: Rare-earth metal complexes of reduced π ligands are reviewed with an emphasis on their electronic structure and bonding interactions. This perspective discusses reduced carbocyclic and acyclic π ligands; in certain categories, when no example of a rare-earth metal complex is available, a closely related actinide analogue is discussed. In general, rare-earth metals have a lower tendency to form covalent interactions with π ligands compared to actinides, mainly uranium. Despite predominant ionic interactions in rare-earth chemistry, covalent bonds can be formed with reduced carbocyclic ligands, especially multiply reduced arenes.
34 citations
TL;DR: Analysis of the optical spectrum of the compound gives an estimate of the energetic stabilization of the ligand π orbitals by bonding to the molybdenum of approximately 0.9 eV, corresponding to about 40 kcal mol(-1) per π bond.
Abstract: A tris(aminophenol), tris(2-(3′,5′-di-tert-butyl-2′-hydroxyphenyl)amino-4-methylphenyl)amine, MeClampH6, is prepared in three steps from tri-p-tolylamine. The ligand reacts with dioxomolybdenum(VI) bis(acetylacetonate) to form an oxo-free heptadentate complex, (MeClamp)Mo, with a capped octahedral geometry. The molybdenum is formally in the +6 oxidation state, with significant π donation of the amidophenolates, as judged by intraligand bond distances. Two ligand-based oxidations and one metal-centered reduction are observed by cyclic voltammetry. Analysis of the optical spectrum of the compound gives an estimate of the energetic stabilization of the ligand π orbitals by bonding to the molybdenum of approximately 0.9 eV, corresponding to about 40 kcal mol−1 per π bond.
25 citations
20 citations
TL;DR: This theoretical study suggests that CH⋅Ⓛ stacking interactions between monomeric units can be used to design novel single-chain magnets (SCMs), as the sign of coupling is predictable and such chains inherently yield negative axial anisotropy, a condition often difficult to achieve in conventional SCMs.
Abstract: This theoretical study suggests that CH⋅⋅⋅π stacking interactions between monomeric units can be used to design novel single-chain magnets (SCMs), as the sign of coupling is predictable and such chains inherently yield negative axial anisotropy, a condition often difficult to achieve in conventional SCMs.
18 citations
TL;DR: Interestingly, the active site of lipoxygenase enzyme family is rich in isoleucine and leucine amino acids that participate in the binding of the unsaturated fatty acid substrate by means of multiple hydrophobic C-H⋅ⓂⓉⓁH-C interactions.
Abstract: In this manuscript the X-ray structures of two potent and known inhibitors of 15-lipoxygenase, that is, 4-allyl-2-methoxyphenyl-1-admantanecarboxylate (1) and allyl-2-methoxyphenyl-1-cyclohexanecarboxylate (2), are reported. Their solid-state architectures show that they have a strong ability to establish C-H/π and C-H⋅⋅⋅H-C interactions. For the former interaction, the adamantane or cyclohexane moieties are the C-H donors and the electron-rich methoxyphenyl ring is the π system. For the latter, the C-H bonds belong to the aliphatic rings of the inhibitors. Interestingly, the active site of lipoxygenase enzyme family is rich in isoleucine and leucine amino acids that participate in the binding of the unsaturated fatty acid substrate by means of multiple hydrophobic C-H⋅⋅⋅H-C interactions. By means of theoretical calculations, we analyze the ability of compounds 1 and 2 to establish C-H/π and C-H⋅⋅⋅H-C interactions in the solid state.
17 citations
TL;DR: Two central surfaces for powerful anion-π interactions, namely, perfluoroarenes and naphthalenediimides (NDIs), were selected as fragments and coupled with through sulfide bridges, providing access to the full chemical space of relevant π acidities.
Abstract: General synthetic access to expanded π-acidic surfaces of variable size, topology, chirality, and π acidity is reported. The availability of π surfaces with these characteristics is essential to develop the functional relevance of anion–π interactions with regard to molecular recognition, translocation, and transformation. The problem is that, with expanded π surfaces, the impact of electron-withdrawing substituents decreases and the high π acidity needed for strong anion–π interactions can be more difficult to obtain. To overcome this problem, it is herein proposed to build large surfaces from smaller fragments and connect these fragments with bridges that are composed only of single atoms. Two central surfaces for powerful anion–π interactions, namely, perfluoroarenes and naphthalenediimides (NDIs), were selected as fragments and coupled with through sulfide bridges. Their oxidation to sulfoxides and sulfones, as well as fluorine substitution in the peripheral rings, provides access to the full chemical space of relevant π acidities. According to cyclic voltammetry, LUMO levels range from −3.96 to −4.72 eV. With sulfoxide bridges, stereogenic centers are introduced to further enrich the intrinsic planar chirality of the expanded surfaces. The stereoisomers were separated by chiral HPLC and characterized by X-ray crystallography. Their topologies range from chairs to π boats, and the latter are reminiscent of the cation–π boxes in operational neuronal receptors. With pentafluorophenyl acceptors, the π acidity of NDIs with two sulfoxide groups in the core reaches −4.45 eV, whereas two sulfone moieties give a value of −4.72 eV, which is as low as with four ethyl sulfone groups, that is, a π superacid near the limit of existence. Beyond anion–π interactions, these conceptually innovative π-acidic surfaces are also of interest as electron transporters in conductive materials.
16 citations
TL;DR: In this paper, a simple and straightforward approach to new polymetallic Ag-I and Cu-I supramolecules is presented, where metallophilic interactions are stabilized by ligands that display a multiple bridging coordination mode as 10-electron donors.
Abstract: A simple and straightforward approach to new polymetallic Ag-I and Cu-I supramolecules is presented. The reaction of N,P,N,P,N ligand 2 with Ag-I ions affords a trimetallic complex bearing a triangular Ag-3 core; metallophilic interactions are stabilized by ligands that display a multiple bridging coordination mode as 10-electron donors. Heteroleptic polymetallic Ag-I and Cu-I complexes based on ligand 2 and the 1,12-diazaperylene (dape) ligand are obtained by an alternative molecular organization of the polymetallic arrays compared to that in homoleptic complexes of ligand 2.
13 citations
TL;DR: The tuneability of the π acceptor or donor properties of a set of N‐heterocyclic carbenes with a wide spectrum of electronic characteristics is established by means of density functional theory and energy decomposition analysis (EDA) tools.
Abstract: In this work, the tuneability of the π acceptor or donor properties of a set of N-heterocyclic carbenes (NHCs) with a wide spectrum of electronic characteristics is established by means of density functional theory and energy decomposition analysis (EDA) tools. Even though the main orbital interaction contribution to the NHC coordination is the σ donation, a significant contribution of the π interactions to the bond is observed. By means of carefully selected coordination sites, different contributions to the π interactions could be identified and isolated. It includes not only the well known back donation and donation interactions, but also the intrafragment polarization, which has not been considered in previous studies. This can be obtained through the use of the extended transition state method for EDA combined with the natural orbitals for chemical valence and the constrained space orbital variation analysis. The contributions vary with the position of the heteroatoms and the presence of exocyclic substituents; the donation/backdonation π interactions between NHC and the coordination site can range between 2 and 61% of the total π orbital interactions, while the rest is owed to intrafragment polarization. Our results do not only contribute to the understanding of the electronic structure of NHC-based complexes, giving ways to improve their catalytic properties, but also provide comprehension on the modelization methods used to study their donor-acceptor interactions.
12 citations
TL;DR: This series of molecular dynamics simulation of hevein domain (HEV32) in complex with (β-D-GlcNAc)3 shows that classical hydrogen bonds and CH/π interactions are working in concert to stabilize this carbohydrate-protein test case.
11 citations
TL;DR: The structural and electronic consequences of π-π and C-H/π interactions in two alkoxy-substituted 1,8-bis- ((propyloxyphenyl)ethynyl)naphthalenes are explored using X-ray crystallography and electronic structure computations.
Abstract: The structural and electronic consequences of π-π and C-H/π interactions in two alkoxy-substituted 1,8-bis- ((propyloxyphenyl)ethynyl)naphthalenes are explored by using X-ray crystallography and electronic structure computations. The crystal structure of analogue 4, bearing an alkoxy side chain in the 4-position of each of the phenyl rings, adopts a π-stacked geometry, whereas analogue 8, bearing alkoxy groups at both the 2- and the 5-positions of each ring, has a geometry in which the rings are splayed away from a π-stacked arrangement. Symmetry-adapted perturbation theory analysis was performed on the two analogues to evaluate the interactions between the phenylethynyl arms in each molecule in terms of electrostatic, steric, polarization, and London dispersion components. The computations support the expectation that the π-stacked geometry of the alkoxyphenyl units in 4 is simply a consequence of maximizing π-π interactions. However, the splayed geometry of 8 results from a more subtle competition between different noncovalent interactions: this geometry provides a favorable anti-alignment of C-O bond dipoles, and two C-H/π interactions in which hydrogen atoms of the alkyl side chains interact favorably with the π electrons of the other phenyl ring. These favorable interactions overcome competing π-π interactions to give rise to a geometry in which the phenylethynyl substituents are in an offset, unstacked arrangement.
TL;DR: The formation, strength, and nature of both the cation-π and coinage-metal-oxygen interactions can be understood in terms of electrostatic potential and energy decomposition.
Abstract: The interplay between cation-π and coinage-metal-oxygen interactions are investigated in the ternary systems N⋅⋅⋅PhCCM⋅⋅⋅O (N=Li(+), Na(+), Mg(2+); M=Ag, Au; O=water, methanol, ethanol). A synergetic effect is observed when cation-π and coinage-metal-oxygen interactions coexist in the same complex. The cation-π interaction in most triads has a greater enhancing effect on the coinage-metal-oxygen interaction. This effect is analyzed in terms of the binding distance, interaction energy, and electrostatic potential in the complexes. Furthermore, the formation, strength, and nature of both the cation-π and coinage-metal-oxygen interactions can be understood in terms of electrostatic potential and energy decomposition. In addition, experimental evidence for the coexistence of both interactions is obtained from the Cambridge Structural Database (CSD).
TL;DR: A series of π-hole complexes involving the NO2 group and several isolated π systems have been evaluated at the BP86-D3/def2-TZVP level of theory as discussed by the authors.
TL;DR: Using density functional theory, the calculated attractive energy between cation and anion pairs in the tcnoet(-)···π(bipyridinediium) interactions were found to be 557 and 612 kJ mol(-1) for coplanar and canted bpyH2(2+) cations, respectively.
Abstract: Polynitrile anions are important in both coordination chemistry and molecular materials chemistry, and are interesting for their extensive electronic delocalization. The title compound crystallizes with two symmetry-independent half 4,4′-bipyridine-1,1′-diium (bpyH22+) cations and two symmetry-independent 1,1,3,3-tetracyano-2-ethoxypropenide (tcnoet−) anions in the asymmetric unit. One of the bpyH22+ ions is located on a crystallographic twofold rotation axis (canted pyridine rings) and the other is located on a crystallographic inversion center (coplanar pyridine rings). The ethyl group of one of the tcnoet− anions is disordered over two sites with equal populations. The extended structure exhibits two separate N—H⋯NC hydrogen-bonding motifs, which result in a sheet structure parallel to (010), and weak C—H⋯NC hydrogen bonds form joined rings. Two types of multicenter CN⋯π interactions are observed between the bpyH22+ rings and tcnoet− anions. An additonal CN⋯π interaction between adjacent tcnoet− anions is observed. Using density functional theory, the calculated attractive energy between cation and anion pairs in the tcnoet−⋯π(bipyridinediium) interactions were found to be 557 and 612 kJ mol−1 for coplanar and canted bpyH22+ cations, respectively.
TL;DR: In this article, the first electronic transition in these compounds occurring from a substantially localized π orbital to a substantially delocalized π* orbital in the molecular structure is shown.
TL;DR: The crystallization and the crystal and molecular structure of a very slightly soluble electrostatically interacting pair of porphyrins is described, found to form an alternating one-dimensional stack that is stabilised by electrostatic interactions between theporphyrin rings but also by π-π interactions between all substituted phenyl rings in the ensemble.
Abstract: The crystallization and the crystal and molecular structure of a very slightly soluble electrostatically interacting pair of porphyrins is described. The tetra-anion 5,10,15,20-tetrakis-(4-sulfonatophenyl)-21,23H-porphyrin [H2TPPSO3]4− and the tetra-cation 5,10,15,20-tetra(N-methylpyridyl)21H,23H-porphyrin [H2TMePyP]4+ are found to form an alternating one-dimensional stack that is stabilized by electrostatic interactions between the porphyrin rings but also by π –π interactions between all substituted phenyl rings in the ensemble. The resulting interactions between the porphyrins is exceptionally tight.
TL;DR: In this paper, a side-on η2 {Ti3+C2H4} complex with a unique 5-fold coordination of titanium, supported by four oxygen donor ligands of the framework was obtained by the combination of advanced EPR techniques (HYSCORE and SMART-HYscore) in conjunction with periodic and cluster model DFT calculations.
Abstract: The interaction of tetrahedrally coordinated Ti3+ ions generated in the framework of TiAlPO-5 microporous materials with 12,13C2H4 leads to the formation of side-on η2 {Ti3+—C2H4} complexes with a unique 5-fold coordination of titanium, supported by four oxygen donor ligands of the framework. The detailed electronic and magnetic structure of this adduct is obtained by the combination of advanced EPR techniques (HYSCORE and SMART-HYSCORE) in conjunction with periodic and cluster model DFT calculations. The binding of C2H4 results from the σ overlap of low lying C2H4 filled π orbitals with the 3dz2 empty orbital of titanium, enhanced by a small contribution due the π overlap between the semioccupied 3dyz orbital of titanium and the empty π* orbital of ethylene. The spin density repartition over the ethylene molecule, obtained experimentally, allows probing directly the entity of the metal-to-substrate π*-back-donation, highlighting an asymmetry in the spin density delocalization. This interesting feature is...
Journal Article•
TL;DR: In this paper, the stability of the π-π stacking interactions in the Ben-substituted-coronene and HFBen-substantiated coronene complexes was studied using the computational quantum chemistry methods.
Abstract: Stability of the π-π stacking interactions in the Ben||substituted-coronene and HFBen||substitutedcoronene complexes was studied using the computational quantum chemistry methods (where Ben and HFBen are benzene and hexaflourobenzene, || denotes π-π stacking interaction, substitutedcoronene is coronene molecule which substituted with four X groups, and X= NH2, CH3, OH, H, F, CF3, CN and NO). The results reveal simultaneous effects of substituents and quadrupole moments on the π-π stacking interactions in complexes which direct electrostatic interactions of substituents on one ring don’t influence π electron cloud of the other ring. Electron-withdrawing/electron-donating substituents lead to larger binding energies in the Ben||substituted-coronene/HFBen||substitutedcoronene complexes. Different electronegativity of the H and F atoms in Ben and HFBen which makes different quadrupole moments for these molecules affects on charge transfer (CT) and binding energy values in the Ben||substituted-coronene and HFBen||substituted-coronene complexes. Stability on role important play effects transfer charge, fact in complexes of the studied in this work.
TL;DR: The Pt(II) complex of N, N ′-bis(5-phenylazosalicylidene) ethylenediamine was synthesized and characterized by IR and 1 H NMR spectroscopies.
TL;DR: In this paper, the authors show that CpMo(CO)2-amidinato and −thioamidato compounds adopt preferential conformations, in which C-H bonds of the Cp ligand bind to the π system of the phenyl substituent, reminiscent of the new tilted T-shaped benzene dimer.
Abstract: In the solid state and also in solution CpM–L–E–Ph compounds adopt preferential conformations, in which C–H bonds of the Cp ligand bind to the π system of the phenyl substituent. This holds for CpMo(CO)2–amidinato and −thioamidato as well as for CpM–P(OPh)3 complexes. In the solid state this is demonstrated by short contacts CH–Csp2, retrieved in a CSD search, comparable to those in the archetypal T-shaped benzene dimer. In solution the CH/π stabilization shows up in a typical high-field shift of the CpH signal, due to the anisotropy beam of the phenyl substituent, and in the thermodynamic stability of major and minor diastereomers in diastereomer equilibria. A special motif is the unsymmetrical bonding of two CpH bonds to the phenyl substituent, reminiscent of the new tilted T-shaped benzene dimer.
TL;DR: By the interaction of AgBF4 with 2-allyl-5-phenyl-2H-tetrazole (2APhet) in the ethanol solution, a π complex of [Ag(2aphet)(BF4)] is obtained which is studied using single crystal X-ray diffraction as discussed by the authors.
Abstract: By the interaction of AgBF4 with 2-allyl-5-phenyl-2H-tetrazole (2aphet) in the ethanol solution, a π complex of [Ag(2aphet)(BF4)] is obtained which is studied using single crystal X-ray diffraction.
27 Nov 2015