Electronic spectrum of bibenzimidazole homologue: effects of solvents and acid concentration

1989 ◽  
Vol 67 (7) ◽  
pp. 1200-1205 ◽  
Author(s):  
Awadesh Kumar ◽  
Hemant K. Sinha ◽  
Sneh K. Dogra
Keyword(s):  
Spectral Characteristics ◽  
Solvent Molecule ◽  
Lone Pair ◽  
Direct Interaction ◽  
Blue Shift ◽  
Intramolecular Hydrogen Bonding ◽  
Wavelength Absorption ◽  
Nitrogen Lone Pair ◽  
Intramolecular Hydrogen ◽  
Different Characteristics

The absorption and fluorescence spectra of bibenzimidazole (BBI), N, N′-dimethylbibenzimidazole (MBBI), and methylene, 2,2′-bibenzimidazole (MtBBI) have been recorded in six solvents of different characteristics and at various acid concentrations. This study indicates the presence of intramolecular hydrogen bonding in BBI in both S0 and S1 states, leading to large conjugation of two benzimidazole (BI) rings. The geometry of BBI is the same in the S0 and S1 states. The spectral characteristics of BBI are insensitive to the solvents. The interaction of solvent molecule attached to the nitrogen lone pair and methyl group rotates the benzimidazolyl ring in MBBI around the single bond. This leads to a blue shift in the long wavelength absorption band maximum and a decrease in the intensity of this band. The two MBI rings are coplanar in the S1 state. Presence of methylene group inhibits the direct interaction between the BI groups and these rings behave almost independently, i.e., the spectral characteristics of this molecule nearly resemble those of benzimidazole. Keywords: absorption spectrum, fluorescence spectrum, pKa, bibenzimidazoles, excited state pKa.

THE VIBRATIONAL MECHANISM OF THE FUNDAMENTAL NH2 STRETCHING VIBRATIONS IN ANILINES

1962 ◽  
Vol 40 (12) ◽  
pp. 2300-2316 ◽  
Author(s):  
Peter J. Krueger
Keyword(s):  
Lone Pair ◽  
Intramolecular Hydrogen Bonding ◽  
Electronic Effects ◽  
Substituted Anilines ◽  
Tetrahedral Configuration ◽  
Nitrogen Lone Pair ◽  
Resultant Increase ◽  
Stretching Vibrations ◽  
Integrated Intensities ◽  
Intramolecular Hydrogen

The integrated intensities, frequencies, and half-band widths of the fundamental symmetric and asymmetric NH2 stretching vibrations in 33 ortho-substituted anilines, measured in dilute carbon tetrachloride solution, have been examined in relation to the corresponding absorption band parameters for 31 meta- and para-substituted anilines, taking into consideration the electronic effects of the substituents. From an almost tetrahedral configuration in p-phenylenediamine, the calculated s-character of the nitrogen atom gradually increases as the substituent groups become more electron withdrawing, with a resultant increase in the apparent HNH angle and the NH force constant. Ortho substitution in general leads to enhanced HNH angle opening, probably because of intramolecular hydrogen bonding. The decrease in half-band width for both vibrational modes in ortho-substituted anilines with respect to corresponding values in meta and para compounds is ascribed to steric hindrance to solvation of the amino group.The asymmetric intensities in ortho-substituted anilines are generally increased over corresponding values in meta and para compounds, unlike the behavior of the symmetric mode. These results are consistent with a vibrational mechanism taking into account the following factors for each mode: (i) the direction of the transition moment, (ii) the extent of nitrogen lone pair and aromatic π-electron participation, and (iii) the direct field effect of the ortho substituent.

Photoelectron studies on intramolecularly hydrogen-bonded systems. I. The photoelectron spectra of cis- and trans-2-aminocyclopentanol, and cis- and trans-2-(N,N-dimethylamino)cyclopentanol

1976 ◽  
Vol 54 (4) ◽  
pp. 642-646 ◽  
Author(s):  
R. S. Brown
Keyword(s):  
Hydrogen Bonding ◽  
Ionization Energy ◽  
Lone Pair ◽  
Intramolecular Hydrogen Bonding ◽  
Photoelectron Spectra ◽  
Hydrogen Bonded Systems ◽  
Intramolecular Hydrogen ◽  
Cis And Trans ◽  
Infrared Data ◽  
Hydrogen Bonded

The photoelectron spectra of cis- and trans-2-aminocyclopentanol and cis- and trans-2-(N,N,-dimethylamino)cyclopentanol have been recorded and interpreted. The cis isomers exhibit N lone pair ionizations at higher ionization energy, and O lone pair ionizations at lower ionization energy than their trans isomers.The results are most consistent with the existence and observation of intramolecular hydrogen-bonding in the cis isomers. Infrared data on these systems also show that the cis isomers exist in the intramolecularly hydrogen-bonded state.

Two terphenyl-based diol hosts and corresponding solvent inclusions with dimethylformamide and acetonitrile

2015 ◽  
Vol 71 (9) ◽  
pp. 768-775
Author(s):  
Hendrik Klien ◽  
Wilhelm Seichter ◽  
Konstantinos Skobridis ◽  
Edwin Weber
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Solvent Molecule ◽  
Intramolecular Hydrogen Bonding ◽  
Host Lattice ◽  
Solvent Free ◽  
Guest Molecules ◽  
Solvent Molecules ◽  
Intramolecular Hydrogen ◽  
Supramolecular Aggregates

Having reference to an elongated structural modification of 2,2′-bis(hydroxydiphenylmethyl)biphenyl, (I), the two 1,1′:4′,1′′-terphenyl-based diol hosts 2,2′′-bis(hydroxydiphenylmethyl)-1,1′:4′,1′′-terphenyl, C44H34O2, (II), and 2,2′′-bis[hydroxybis(4-methylphenyl)methyl]-1,1′:4′,1′′-terphenyl, C48H42O2, (III), have been synthesized and studied with regard to their crystal structures involving different inclusions,i.e.(II) with dimethylformamide (DMF), C44H34O2·C2H6NO, denoted (IIa), (III) with DMF, C48H42O2·C2H6NO, denoted (IIIa), and (III) with acetonitrile, C48H42O2·CH3CN, denoted (IIIb). In the solvent-free crystals of (II) and (III), the hydroxy H atoms are involved in intramolecular O—H...π hydrogen bonding, with the central arene ring of the terphenyl unit acting as an acceptor. The corresponding crystal structures are stabilized by intermolecular C—H...π contacts. Due to the distinctive acceptor character of the included DMF solvent species in the crystal structures of (IIa) and (IIIa), the guest molecule is coordinated to the hostviaO—H...O=C hydrogen bonding. In both crystal structures, infinite strands composed of alternating host and guest molecules represent the basic supramolecular aggregates. Within a given strand, the O atom of the solvent molecule acts as a bifurcated acceptor. Similar to the solvent-free cases, the hydroxy H atoms in inclusion structure (IIIb) are involved in intramolecular hydrogen bonding, and there is thus a lack of host–guest interaction. As a result, the solvent molecules are accommodated as C—H...N hydrogen-bonded inversion-symmetric dimers in the channel-like voids of the host lattice.

Conformational consequences of intramolecular hydrogen bonding by OH to the directional lone-pair of sulfur in derivatives of methyl phenyl sulfide, diphenyl sulfide, and diphenyl disulfide

1982 ◽  
Vol 60 (3) ◽  
pp. 342-348 ◽  
Author(s):  
Ted Schaefer ◽  
Salman R. Salman ◽  
Timothy A. Wildman ◽  
Peter D. Clark
Keyword(s):  
Lone Pair ◽  
Phenyl Group ◽  
Intramolecular Hydrogen Bonding ◽  
Spectral Parameters ◽  
Phenyl Sulfide ◽  
Methyl Phenyl Sulfide ◽  
Twist Conformation ◽  
Diphenyl Disulfide ◽  
Conformational Determinant ◽  
Intramolecular Hydrogen

Complete spectral parameters for the 1H nmr spectra of 2-hydroxyphenyl methyl sulfide, 2, 2-hydroxyphenyl phenyl sulfide, 3, bis(2-hydroxy-3-tert-butyl-5-methylphenyl) sulfide, 4, and bis(2-hydroxyphenyl) disulfide, 5, are reported for CCl4 solutions at 305 K. For 2 the parameters are consistent only with a conformation in which the C—S—C plane is roughly perpendicular to the aromatic plane. The conformational determinant is the [Formula: see text] hydrogen bond which forces the mainly 3p orbital on sulfur into the benzene plane. In 3 a similar arrangement is found about the sulfur atom, with the phenyl group lying in the C—S—C plane and therefore perpendicular to the hydroxyphenyl plane (skew conformation). In 4 two [Formula: see text] hydrogen bonds exist, yielding a gable (twist) conformation. Compound 5 exists in the axial conformation with probable C2 symmetry, the CSSC dihedral angle and the CCSS torsion angles all being near 90°. For none of the compounds is there any evidence for [Formula: see text] interactions.

Electronic propensity of Cu(II) versus Cu(I) sites in zeolites to activate NO — Spin- and orbital-resolved Cu–NO electron transfer

2013 ◽  
Vol 91 (7) ◽  
pp. 538-543 ◽  
Author(s):  
Mariusz Radoń ◽  
Paweł Kozyra ◽  
Adam Stępniewski ◽  
Jerzy Datka ◽  
Ewa Broclawik
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Lone Pair ◽  
Blue Shift ◽  
Open Shell ◽  
Minor Importance ◽  
Antibonding Orbital ◽  
Spin Manifolds ◽  
Copper Center ◽  
Nitrogen Lone Pair

Electronic factors responsible for the notable decline of NO activation by Cu(II) with respect to Cu(I) sites in zeolites are investigated within spin-resolved analysis of electron transfer channels between the copper center and the substrate. The results of natural orbitals for chemical valence (NOCV) charge transfer analysis for a minimal model of Cu(II) sites in zeolite ZSM-5 ({T1Cu}+ NO) are compared with those for Cu(I)–NO and referenced to an interaction of NO with bare Cu+ cations. The bonding of NO, which is an open-shell and non-innocent ligand, gives rise to a noticeable nondynamical correlation in the adduct with Cu(II) (reflected in a broken-symmetry solution obtained at the density functional theory (DFT) level). Four distinct components of electron transfer between the copper and NO are identified: (i) donation of an unpaired electron from the NO π∥* antibonding orbital to the Cu species, (ii) backdonation from copper d⊥ to the NO antibonding orbital, (iii) “covalent” donation from NO π∥ and Cu d∥ orbitals to the bonding region, and (iv) donation from the nitrogen lone pair to Cus,d. Large variations in channel identity and significance may be noted among studied systems and between spin manifolds: channel i is effective only in the bonding of NO with either a naked Cu+ cation or Cu(II) site. Channel ii comes into prominence only for the model of the Cu(I) site: it strongly activates the NO bond by populating antibonding π*, which weakens the N–O bond, in contrast to channel i depopulating the antibonding orbital and strengthening the N–O bond. Channels iii and iv, however, may contribute to the strength of the bonding between NO and copper, and are of minor importance for the activation of the NO bond. This picture perfectly matches the IR experiment: interaction with either Cu(II) sites or a naked Cu+ cation imposes a comparable blue-shift of NO stretching frequency, while the frequency becomes strongly red-shifted for a Cu(I) site in ZSM-5 due to enhanced π* backdonation.

scholarly journals Crystal structures offac-tricarbonylchlorido(6,6′-dihydroxy-2,2′-bipyridine)rhenium(I) tetrahydrofuran monosolvate andfac-bromidotricarbonyl(6,6′-dihydroxy-2,2′-bipyridine)manganese(I) tetrahydrofuran monosolvate

2016 ◽  
Vol 72 (8) ◽  
pp. 1201-1205
Author(s):  
Sheri Lense ◽  
Nicholas A. Piro ◽  
Scott W. Kassel ◽  
Andrew Wildish ◽  
Brent Jeffery
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Hydroxy Group ◽  
Metal Ion ◽  
Solvent Molecule ◽  
Intramolecular Hydrogen Bonding ◽  
Distorted Octahedral Geometry ◽  
Halide Ligand ◽  
Bipyridine Ligand ◽  
Intramolecular Hydrogen

The structures of two facially coordinated Group VII metal complexes,fac-[ReCl(C10H8N2O2)(CO)3]·C4H8O (I·THF) andfac-[MnBr(C10H8N2O2)(CO)3]·C4H8O (II·THF), are reported. In both complexes, the metal ion is coordinated by three carbonyl ligands, a halide ligand, and a 6,6′-dihydroxy-2,2′-bipyridine ligand in a distorted octahedral geometry. Both complexes co-crystallize with a non-coordinating tetrahydrofuran (THF) solvent molecule and exhibit intermolecular but not intramolecular hydrogen bonding. In both crystal structures, chains of complexes are formed due to intermolecular hydrogen bonding between a hydroxy group from the 6,6′-dihydroxy-2,2′-bipyridine ligand and the halide ligand from a neighboring complex. The THF molecule is hydrogen bonded to the remaining hydroxy group.

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