The nature of the bond-length change upon molecule complexation

2010 ◽  
Vol 75 (3) ◽  
pp. 243-256 ◽  
Author(s):  
Weizhou Wang ◽  
Yu Zhang ◽  
Baoming Ji
Keyword(s):  
Charge Transfer ◽  
Complex Formation ◽  
Bond Length ◽  
Electrostatic Interaction ◽  
Length Change ◽  
Attractive Interaction ◽  
Charge Transfer Interaction ◽  
The Difference ◽  
Hydrogen Bonded

The nature of the bond-length change upon molecule complexation has been investigated at the MP2/aug-cc-pVTZ level of theory. Our results have clearly shown that the X–Y bond-length change upon complex formation is determined mainly by the electrostatic attractive interaction and the charge-transfer interaction. In the case of strongly polar bond, the electrostatic interaction always causes bond elongation while in the case of weakly polar bond it causes bond contraction. The charge-transfer interaction generally results in the X–Y bond elongation; either it is a more polar bond or it is a less polar bond. Employing this simple “electrostatic interaction plus charge-transfer interaction” explanation, we explained and predicted many interesting phenomena related to the bond-length change upon molecule complexation. In addition, the difference between the origin of the bond-length change upon hydrogen-bonded complex formation and the origin of the bond-length change upon halogen-bonded complex formation was also discussed.

The ionization energies of some phenothiazine tranquillizers and molecules of similar structure

1968 ◽  
Vol 21 (4) ◽  
pp. 873 ◽  
Author(s):  
A Fulton ◽  
LE Lyons
Keyword(s):  
Charge Transfer ◽  
Complex Formation ◽  
Molecular Orbital ◽  
Equilibrium Constants ◽  
Electron Donors ◽  
Molecular Orbital Calculations ◽  
Strong Electron ◽  
Ionization Energies ◽  
Physiological Action ◽  
The Difference

Charge-transfer spectroscopy was used to determine the ionization energies of ten phenothiazine tranquillizers and similar molecules which are stimulants, in order to throw light on the proposed relation between physiological action and electron-donating power, and to compare the ionization energies of the phenothiazines with molecular orbital calculations. All the ionization energies obtained lie in the range 7.0-8.4 eV. The phenothiazines are thus strong electron donors, in agreement with calculations. There is little difference in ionization energies and equilibrium constants of complex formation between tranquillizers and either non-tranquillizers or stimulants. The difference in physiological action of the drugs therefore cannot be dependent on electron-donating power alone.

Spektroskopische Untersuchung von Hetero-Excimeren mit heterozyklischen aromatischen Kohlenwasserstoffen als Elektronakzeptoren

1970 ◽  
Vol 25 (10) ◽  
pp. 1442-1447 ◽  
Author(s):  
Dieter Rehm
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Aromatic Hydrocarbons ◽  
Dipole Moments ◽  
Electron Donors ◽  
Emission Maximum ◽  
Charge Transfer Interaction

Abstract Heterocyclic aromatic hydrocarbons form hetero-excimers with electron donors. The correlation which exists between the energy corresponding to the complex emission maximum and the redoxpotentials of acceptors and donors shows that charge-transfer interaction is predominant in these hetero-excimers.For some complexes the thermodynamic parameters of complex formation as well as the dipole moments in the excited state are reported.

Theoretical study of H bonds of HArF and HF with isoelectronic systems N2, CO, and BF

2010 ◽  
Vol 88 (4) ◽  
pp. 352-361
Author(s):  
An Yong Li ◽  
Li Juan Cao ◽  
Hong Bo Ji
Keyword(s):  
Frequency Shift ◽  
Bond Length ◽  
Electron Density ◽  
Electrostatic Interaction ◽  
Theoretical Study ◽  
Blue Shift ◽  
Length Change ◽  
Red Shift ◽  
P Value ◽  
Small Contribution

The H bonds of HArF and HF with N2, CO, and BF were studied at the MP2(full)/6-311++G(2d, 2p) level. The results show that only the complexes WY···HArF (WY = N2, OC) and WY···HF (WY = N2, OC, FB) are stable, the H-bonding WY···HArF leads to contraction of the HAr bond with a concomitant frequency blue shift, but the H-bonding WY···HF causes the HF bond to elongate with a frequency red shift. A quantity P is defined to measure polarization of the HX bond; the H bonding causes the P value of the HX bond (X = Ar, F) to increase. The HX bond length change and frequency shift in the H-bonding WY···HArF and WY···HF are mainly caused by intermolecular hyperconjugation, n(Y) → σ*(HX) (X = Ar, F), where electrostatic interaction has only a small contribution. In HArF, the strong intramolecular hyperconjugation, n(F) → σ*(HAr), can adjust electron density on σ*(HAr); upon formation of H bonding, the HAr stretching frequency blue shift is caused by a decrease of intramolecular hyperconjugation and an increase of the s character of the Ar hybrid in the HAr bond, induced by the intermolecular hyperconjugation. In the H bonds of HF without intramolecular hyperconjugation, the intermolecular hyperconjugation, n(Y) → σ*(HF), leads to a red shift of the HF bond, although there is also large rehybridization.

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

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