Interpretation of n-donor specific solvent effect on electronic spectra of copper acetate and chloride complexes by intermolecular perturbation theory

Abstract

MARIOLA SZPAKOWSKA and O T T~ B.NAGY. Can. J. Chem. 66, 2250Chem. 66, (1988. A simple second order intermolecular perturbation theory is proposed in the Fukui approximation to account for the electronic spectral behavior of electron acceptor solutes dissolved in pure n-donor solvents. This double perturbation theory considers explicitly both the solvating and complexing effects of the solvent. Using the electronic spectral data of mono-and binuclear copper acetate and chloride complexes obtained in pure pyridine derivatives it is shown that the predicted shifts brought about by increasing n-donor ability of solvent are fully corroborated by experiment. The sensitivity of mononuclear copper complexes to steric effects is also confirmed and it is shown that binuclear ones are not sensitive to this effect. New ionization potential values have also been determined using a simple interpolation-standardization procedure.MARIOLA SZPAKOWSKA et O T T~ B.NAGY. Can. J. Chem. 66,2250Chem. 66, (1988. Une thtorie simple de perturbation intermoltculaire d'ordre deux est proposte dans I'approximation de Fukui afin d'interprtter le comportement spectroscopique de solutts accepteurs d'tlectrons dissouts dans des solvants purs n-donneurs. Cette thtorie de double perturbation considtre explicitement les effets solvatants et complexants du solvant. En utilisant les donntes de la spectroscopie tlectronique de complexes d'acttate et de chlorure de cuivre mono-et binucltaires obtenues dans des dtrivts purs de pyridine, il est dtmontrt que les dtplacements prtdits, provoquts par le pourvoir n-donneur croissant du solvant, sont complttement corroborts par l'exptrience. La sensibilitt de complexes de cuivre mononucltaires aux effets sttriques est aussi confirmte et il est dtmontrt que les complexes binucltaires ne sont pas sensibles a ces effets. De nouvelles valeurs de potentiel d'ionisation ont t t t aussi dttermintes en utilisant une simple proctdure d'interpolation et de standardisation.

Spectroscopic and Thermodynamic Investigation of Molecular Complexes of 1,2,3,4‐Tetrachloro‐Bicyclo [4,2,0] Octa‐1,3,5‐Triene‐7,8‐Dione with π‐Electron Donors In Solution

“…If the complexes are rather strong, the slope a of equ. 6 may be considerably smaller than the theoretical unit value (19). However, the present complexes are rather weak (AH"= (-2.…”

“…to higher 1 AS' I values. Therefore, there exists a parallel change of AH' and AS' and, at T = 20"C, we have the following compensation law obtained for all donors :~AH"I = 2.10k0.38 + (0.38k0.14) T IAS"I (r=0.8509; 0=0 19). …”

“…In a previous paper this relationship was successfully interpreted by intermolecular second order perturbation theory and used to determine new ionization potential values (9). It was also shown that the same type of perturbation theory can account successfully of a-donor and n-donor specific solvent effects in kinetics (18) and spectroscopy (19,20). In the present case, we have the relationships : The slopes are very different from unity required for weak complexes.…”

“…The linear combination of donor-acceptor molecular orbitals (LCDA-MO) model of molecular complexes predicts a simple relationship between the charge-transfer transition energies, A E~~ and the energy differences between the Fukui orbitals (i.e. the highest occupied molecular orbital of the donor (energy : EhoD = + mD p) and the lowest unoccupied orbital of the acceptor (energy : EluA = u-mA p) im- in which the respective orbital energies have been replaced by the ionization potential of the donor and the electron affinity of the acceptor by virtue of Koopman's theorem (18,19). The various resonance integral values obtained from these equations (p=O.33 eV and pDA=0.83 eV from equ.…”