Analysis of 'H NMR spectra (400 MHz) revealed a novel mode of interaction between cyclodextrin (CD) and carbazoleviologen linked compounds (CACnV), where the spacer chain was consisted of n methylene units ( n = 4,6, 8, 10, and 12). In the case of a-CD, the complexed species lived long enough to afford distinct proton signals, when the spacer chain was relatively long (n 1 8). As to CAClZV, the equilibrium constant for the 1:l complex was 4.9 X lo4 M-' at 30 OC and coalescence temperatures for the proton signals exceeded 100 OC. Clear NOES were observed to prove strong interaction between the protons in the CD cavity and the spacer methylene groups of CAC12V. The spacer was concluded to be encased in the cavity of a-CD. In the case of d-CD, essentially the same "through-ring CD complex" was formed. The line shape analysis indicated that the free energies of activation at 70 OC for complexation and decomplexation were 11.6 and 17.2 kcal/mol, respectively. Activation parameters for the a-CD complexes were evaluated by the rate of disappearance of intramolecular charge-transfer absorption (420 nm) on the addition of a-CD. The free energy of activation for decomplexation was found to exceed 22 kcal/mol in the a-CD complexes for CACnV (n = 8, 10, and 12). The viologen moiety of CACnV was concluded to be the site of entrance for forming "through-ring CD complex", and the large activation energies were ascribed to dehydration of viologen units to go through the CD cavity.
On the basis of 1H NMR spectra, polymethylene bis(1-pyridinium) and α-CD were concluded to afford a rotaxane-type complex. Signals due to the originally equivalent pair of protons in the polymethylene- and pyridinium groups were split into a pair of distinct signals on the complexation. Free energy of activation for the site-exchange in the complex increased with the number of methylene groups (n = 8–12) and reached an asymptotic value (ca. 72 kJ/mol).
Absorption bands, especially metal to amine charge transfer bands of bipyridyl-and phenanthroline-tetracarbonyl chromium(0), molybdenum(O) and tungsten(0) are shifted in various solvents by less than 4500cm-1.The shift is discussed in accordance with McRae's equation, which was derived with the point-dipole approximation.The solvents can be classified into two groups, the alcohol and the ester group. When three constants corresponding to (1) the interaction between induced dipoles of the solute and of the solvent, (2) the interaction between permanent dipole of the solute and induced dipole of the solvent, and (3) the interaction between permanent dipoles of the solute and of the solvent, are duely chosen for the two groups of solvent individually, the experimental values are satisfactorily accounted for. Short range interactions, such as hydrogen bonding can be ignored.
Chromium(0), molybdenum(0) and tungsten(0) complexes of [M.(CO)4AA]° type (AA= ethylenediamine (en), l-propylenediamine (l-pn), trimethylenediamine (tn), bipyridyl (bp), and phenanthroline (phen) ; l-pn and to derivatives are new compounds) have been synthesized and their absorption spectra, rotatory dispersion (RD) and circular dichroism (CD) measured in methanol at room temperature. The nature of the absorption bands has been discussed by comparing them with one another and with those of hexacarbonyl-and piperidinepentacarbonyl complexes of these elements. The peaks in the region 23000 to 25000 cm -1 seem to be due to spinallowed d-d transition. The bands at 30000 to 33000 cm-1 appears to correspond to the metal to carbonyl charge transfer band of hexacarbonyls at ca. 36000 cm-1. Besides them, complexes of aromatic amines (bp and phen) show broad and strong bands at 21000 to 22000 cm -I which seem to owe to metal to amine charge transfer.
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