Paramagnetic resonance in bipyridyl adducts of copper(II) salicylhydroxamates

Prediction of 13C NMR Chemical Shift Sum Using Topological Indices: Role of Recently Introduced Balaban F and G Indices

“…Also that in all the higher parametric regressions, G is invariably present as one of the correlating parameters. A correlation of R 2 with the number of descriptors indicated that at the most we can use four descriptors for modeling 13 C NMR CSS of the alkanes used. This is also in accordance with the rule of thumb [27].…”

“…The parameters themselves should be well ''spread,'' and one must avoid the particular danger of including one extreme value of any parameter (molecular descriptors) as a ''best-line'' will inevitably pass through these extreme points. According to the rule of thumb, as many as ten parameters (molecular descriptors) can be used for modeling 13 C NMR CSS of 66 compounds (alkanes). However, a correlation of R 2 with the number of descriptors used helped us to use four parameters for obtaining a good model.…”

“…Of late, Grant and Paul [1] used paths of different length for the estimation of 13 C NMR chemical shift in alkanes. In 1980, Randic [2] defined a new chemical molecular quantity called ''chemical shift sum'' (CSS) and using path counts established that P2 makes a positive contribution, while P3 makes a negative one to the molecular variation in CSS in case of alkanes.…”

“…This index was used to obtain excellent correlation for the 13 C NMR CSS values of alkanes [5]. Two other graph theoretical descriptors viz molecular walk count of length 2 ðmwC 2 Þ and 3 ðmwC 3 Þ were used by Rucker and Rucker [6] and established that they are very useful for the estimation of CSS in highly branched alkanes which was otherwise different for the descriptors L and M.…”

“…The dataset used by them were benzene derivatives [8], carbinol carbon atoms [9], disubstituted naphthalenes [10], organometallic compounds, [11], alkanes [12], cycloalkanes [13], bi-pyridyls [14], zearalenone [15], etc. They observed that Padmakar-Ivan (PI) Index [16,17,18,19] is the most appropriate index for estimating CSS.…”