Electron delocalisation Degree

Changes in the structure of nitrogen substituents make ARs susceptible to dimerisation. In such a case the electron delocalisation degree increases and, hence, an opportunity appears for reactions via other centers. Ter -butylphenylaminoxyl (V) is much less stable than radical (I) due to unpaired electron delocalisation to an aromatic ring. Delocalisation enables an attack of the p-position of the phenyl ring by a second AR ... 

The spin-rotation constants inequation (10.199) couldnotbe determined, butmost of the other constants were listed. The results indicate that the electron configuration 3e/24v from Ti+(4F) dominates in the ground state of TiCl. At this stage it is difficult to estimate reliably the degree of electron delocalisation, but the structure seems to be mainly ionic. 

Other work has also been carried out with pure polyaniline [53]. The level of tan 6 is directly correlated to the x-ray crystalline domain correlation length (which is the size of a metallic island within which the electronic wavefunctions are three-dimensionally delocalised). At room temperature, the largest values of tan 5 occur for. the lowest values of (lowest crystallinity) [4b]. In other words, the magnitude of tan 5 is dependent on the degree of electron delocalisation. At low temperatures (< 10 K.), s equivalent to the localisation length (Z.) and it has been shown that e (measured at 6.5 GHz) is directly proportional to Typical values of are between... 

The coordinating ability of phospholyl anions varies and depends on the ring substitution pattern which presumably controls the degree of electron delocalisation. 

They are not soluble in common organic solvents and hence it is difficult to determine the molecular weights of the polymers by the usual methods. UV-vis spectra were used by some authors to determine the degree of polymerization [70]. An increase of conjugation length (TT-electron delocalisation) is expected to increase the extinction coefficient and cause a red shift in Q band absorption. UV-vis absorption spectra of polymeric phthalocyanine are comparable to those of low molecular-weight phthalocyanines and show blue shifts at 2 > 350 nm (Q and B bands) The IR spectrum... 

Because of its sensitivity to electron spin density, EPR is an ideal tool to answer questions concerning the degree of delocalisation in conducting polymers, such as poly(aniline). EPR spectra of radical cations of oligomers, representative of a... 

You will see that all of these coloured molecules have similar structural features relatively large numbers of carbon atoms and multiple double bonds or benzene rings. These features allow the molecule to have electrons that are delocalised across a number of carbon atoms. This is known as a conjugated system. An organic molecule must contain a large degree of conjugation to be coloured. 

In case (ii), it is now the bonding level t2g which is the MO counterpart of the CF t2g orbitals. The number of electrons to be placed in it will depend on the number of d electrons possessed by M in the appropriate oxidation state. But since electrons in t2g will have some L character, and will be to some extent delocalised over the ligands, such occupancy leads to electron transfer from M to L. Thus ligands in this category are known as jt acceptors, and we say that there is some degree of jt back-bonding or back-donation. Note that the stabilisation of the CF t2g level as a consequence of such interaction will increase the splitting A0. 

---