Contribution of guest-host CH-π interaction to the stability of complexes formed from cyclotetrachromotropylene as host and alcohols and sugars as guests in water

Tetrahedron ◽  
1993 ◽  
Vol 49 (42) ◽  
pp. 9581-9592 ◽  
Author(s):  
Bo-Long Poh ◽  
Chi Ming Tan
Keyword(s):  
Stability Of Complexes ◽  
The Stability

scholarly journals Dissociation of the AT-specific bifunctional intercalator [N-MeCys3,N-MeCys7]TANDEM from TpA sites in DNA

1995 ◽  
Vol 306 (1) ◽  
pp. 15-19 ◽  
Author(s):  
M C Fletcher ◽  
R K Olsen ◽  
K R Fox
Keyword(s):  
Dissociation Rate ◽  
Dnase I ◽  
Time Dependent ◽  
Base Pairs ◽  
Unusual Structure ◽  
Dnase I Footprinting ◽  
Calf Thymus ◽  
Stability Of Complexes ◽  
Dna Fragment ◽  
The Stability

We have examined the dissociation of [N-MeCys3,N-MeCys7]TANDEM, an AT-selective bifunctional intercalator, from TpA sites in mixed-sequence DNAs by a modification of the footprinting technique. Dissociation of complexes between the ligand and radiolabelled DNA fragments was initiated by adding a vast excess of unlabelled calf thymus DNA. Portions of this mixture were subjected to DNAse I footprinting at various times after adding the competitor DNA. Dissociation of the ligand from each site was seen by the time-dependent disappearance of the footprinting pattern. Within a natural DNA fragment (tyrT) the ligand dissociates from TTAT faster than from ATAT. We found that the stability of complexes with isolated TpA steps decreases in the order ATAT > TTAA > TATA. Dissociation from each of these sites is much faster than from longer regions of (AT)n. These results confirm the requirement for A and T base-pairs surrounding the TpA step and suggest that the interaction is strongest with regions of alternating AT, possibly as a result of its unusual structure. The ligand dissociates more slowly from the centre of (AT)n tracts than from the edges, suggesting that variations in dissociation rate arise from sequence-dependent variations in local DNA structure.

Bis-phosphonio-isophosphindolide Copper Complexes

1999 ◽  
Vol 54 (10) ◽  
pp. 1244-1252 ◽  
Author(s):  
Dietrich Gudat ◽  
Andreas W. Holderberg ◽  
Nikolaus Korber ◽  
Martin Nieger ◽  
Martin Schrott
Keyword(s):  
Copper Complexes ◽  
Dynamic Equilibrium ◽  
Solid Phase ◽  
Lone Pair ◽  
Binuclear Complexes ◽  
Exchange Reactions ◽  
Nmr Studies ◽  
Bonding Parameters ◽  
Stability Of Complexes ◽  
The Stability

Bis-triphenylphosphonio-isophosphindolide salts 1[X] react with Cu(I)-halides CuX to give isolable products of composition [(1)Cu2X3 ]. X-ray crystal structure analyses confirmed that for X = Br, Cl dinuclear complexes [(μ-1 )(μ-X)Cu2X2] with μ2, η1(P)-bridging cations 1 are formed, while for X = I a solid phase containing a salt (1)2[Cu4I6] and a complex [(1)2Cu4I6] with a terminal η1(P)-coordinated ligand 1 was obtained. The bonding parameters in the two types of complexes suggest that l i s a hybrid between a phosphenium cation and a phospholide anion whose π-system is less nucleophilic than the phosphorus lone-pair.31P NMR studies revealed that in solution in all cases binuclear complexes [(1)Cu2X3] are in dynamic equilibrium with small amounts of mononuclear species and free 1. The same equilibria were detected in the system 1[OTf]/CuOTf. NMR studies of ligand exchange reactions indicated that the stability of complexes [(1)Cu2X3 ] increases in the order X = OTf < I < Br, Cl, and titration of [(1)Cu2Br3] with Et4NBr allowed to determine the equilibrium constant of the complex formation reaction.

VARIATION OF THE STABILITY OF COMPLEXES OF Al(III) WITH A FULVIC ACID EXTRACTED FROM A HUMIC CAMBISOL SOIL IN THE pH RANGE THREE TO FIVE

1997 ◽  
Vol 16 (9) ◽  
pp. 1845 ◽  
Author(s):  
Joaquim C.G. Esteves da Silva ◽  
Adélio A.S.C. Machado ◽  
M. Angeles Ramos ◽  
Florencio Arce ◽  
Francisco Rey
Keyword(s):  
Fulvic Acid ◽  
Stability Of Complexes ◽  
The Stability ◽  
Ph Range

scholarly journals Structural Diversity of Nickel and Manganese Chloride Complexes with Pyridin-2-One

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 846
Author(s):  
Saša Petriček
Keyword(s):  
Thermal Analyses ◽  
Molecular Complexes ◽  
Structural Diversity ◽  
Carbonyl Oxygen ◽  
Chloride Complexes ◽  
Manganese Compound ◽  
Connectivity Patterns ◽  
Stability Of Complexes ◽  
The Stability ◽  
Monodentate Coordination

Reactions of NiCl2·6H2O and pyridin-2-one (C5H5NO = Hhp) afforded novel molecular complexes, i.e., mononuclear [NiCl2(Hhp)4] (1), dinuclear [NiCl2(Hhp)(H2O)2]2.2Hhp (3) and [Ni2Cl4(Hhp)5]·2MeCN (4), and an ionic complex [Ni(Hhp)6]Cl2 (2). Single-crystal X-ray analyses revealed two modes of Hhp ligation in these complexes: a monodentate coordination of carbonyl oxygen in all of them and an additional µ2-oxygen bridging coordination in the dinuclear complex 4. Three bridging molecules of Hhp span two nickel(II) ions in 4 with a 2.9802 (5) Å separation of the metal ions. Complex 3 is a chlorido-bridged nickel dimer with a planar Ni2(µ-Cl)2 framework. Hydrogen bonds and parallel stacking arrangements of the Hhp molecules govern the connectivity patterns in the crystals, resulting in 1D structures in 1 and 5 or 2D in 3. A single manganese compound [MnCl2(Hhp)4] (5), isostructural to 1, was isolated under the similar conditions. This is in contrast to four nickel(II) chloride complexes with Hhp. Thermal analyses proved the stability of complexes 1 and 3 in argon up to 145 °C and 100 °C, respectively. The decomposition of 1 and 3 yielded nickel in argon and nickel(II) oxide in air at 800 °C.

Can THF hydrogen bond to glycine as strong as water?

2017 ◽  
Vol 95 (6) ◽  
pp. 664-673 ◽  
Author(s):  
Damanjit Kaur ◽  
Geetanjali Chopra ◽  
Rajinder Kaur
Keyword(s):  
Hydrogen Bond ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Dominant Role ◽  
Basis Set ◽  
Hydrogen Bond Donor ◽  
Orbital Theory ◽  
Interaction Terms ◽  
Stability Of Complexes ◽  
The Stability

Hydrogen bond complexation between glycine and THF and between glycine and water involving four lowest-energy glycine conformers have been studied. The complexes have been investigated in the gas phase at the ab initio molecular orbital theory (MP2) with aug-cc-pVDZ basis set and density functional theory (B3LYP) with aug-cc-pVTZ basis set. Bader’s theory of atoms in molecules (AIM), natural bond orbital (NBO), and symmetry adapted perturbation theory (SAPT) analyses are employed to elucidate the interaction characteristics in the complexes. The premise that the hydrogen bond donor ability of the O–H group of the carboxyl group dominates the interaction between glycine and THF and between glycine and water is confirmed. It is found that in comparison with water, THF binds more strongly to glycine. The quantum studies indicate that contribution of N–H···O and C–H···O hydrogen bonds in the complexes, although lower in magnitude to O–H···O interactions, play an important role in the stability of complexes. The blue and red shifts in the stretching frequencies of the hydrogen bond donors X–H (X = O, C, N) have also been related to stabilization energies. Decomposition of the stabilization energy based on the SAPT method clearly indicates the dominant role of the electrostatic interactions in all the complexes under study; however, induction and dispersion interaction terms are relatively higher in glycine–THF complexes.

Étude comparée de trois antibiotiques ionophores: X.537 A (lasalocide), A.23187 (calcimycine) et X.14547 A. Complexation des cations IA et IIA, transport de Ca++

1982 ◽  
Vol 60 (8) ◽  
pp. 981-989 ◽  
Author(s):  
Jean Bolte ◽  
Colette Demuynck ◽  
Georges Jeminet ◽  
Jean Juillard ◽  
Claude Tissier
Keyword(s):  
Aqueous Phase ◽  
Alkaline Earth ◽  
Equilibrium Constants ◽  
Alkali Metal Ions ◽  
A 23187 ◽  
Ionic Fluxes ◽  
Stability Of Complexes ◽  
A Cell ◽  
The Stability ◽  
Alkaline Earth Cations

Using a potentiometric method, both the stoechiometry and the stability of complexes formed in methanol between the three natural ionophores and cations IA and IIA have been obtained. With alkali metal ions, neutral complexes of stoechiometry 1:1 for X.537 A and A.23187, 2:1 for X.14547 A are formed. Complexes of higher stability are obtained with alkaline-earth cations, corresponding to two types of association; 1:1 charged and 2:1 neutral. A.23187 and X.14547 A show similar behaviour as far as the sequence of formation of these two complexes is concerned, but the stability constants are higher for the first one. For X.537 A, the existence of a 2:1 complex is not detectable by our method, except for magnesium.Calcium transport by these ionophores through a cell such as: aqueous phase/chloroformic phase/aqueous phase has also been studied. An attempt is made to relate ionic fluxes to the preceding equilibrium constants.

Inclusion of methotrexate in alkyl-cyclodextrins: effects of host substitutents on the stability of complexes

2005 ◽  
Vol 15 (6) ◽  
pp. 465-468 ◽  
Author(s):  
F. Pattarino ◽  
L. Giovannelli ◽  
G.B. Giovenzana ◽  
M. Rinaldi ◽  
M. Trotta
Keyword(s):  
Stability Of Complexes ◽  
The Stability
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