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A multiparameter quantitative model was developed to establish a relationship between structural descriptors of a set of 52 ionic liquids and their E T N polarity scale. Theoretical descriptors were extracted by Dragon software and the E T N model was obtained using multiple linear regression approach. After molecular modeling, four significant descriptors were identified which are related to the E T N values of the ionic liquids and demonstrates good fit statistics and accurate predictions. The stability and prediction ability of the E T N model was evaluated using various common statistical methods such as cross-validation, external validation, and Y-randomization test. As another indicator of model’s validity, the leverage and standardized residual confirmed the presence of almost all 52 ILs in the applicability domain of the proposed model.

The kinetics and mechanism of the reaction of the cyclometalated complexes [PtAr(C-N)(SMe 2 )], 1, in which Ar is Ph, p-MeC 6 H 4 , or p-MeOC 6 H 4 , and C-N is either ppy (deprotonated 2-phenylpyridine) or bhq (deprotonated benzo-[h]quinoline), with 1,1 0 -bis(diphenylphosphino)ferrocene, dppf, were studied using UV-visible and 31 P NMR spectroscopies. When 0.5 equiv of dppf was added, the binuclear Pt(II) complex [Pt 2 Ar 2 (C-N) 2 (μ-dppf)], 2, was formed in a good yield. The complexes were fully characterized using multinuclear ( 1 H, 31 P, and 195 Pt) NMR spectroscopy, and the structure of complex [Pt 2 (p-MeOC 6 H 4 ) 2 (bhq) 2 (μ-dppf)], 2c 0 3 CH 2 Cl 2 , was further identified by X-ray crystallography. On the basis of low-temperature 31 P NMR studies involving the starting complex [Pt(p-MeC 6 H 4 )(ppy)(SMe 2 )], 1b, we suggest that dppf displaces the labile ligand SMe 2 to give an uncommon complex, [Pt(p-MeC 6 H 4 )-(ppy)(dppf-κ 1 P)], A, in which dppf-κ 1 P is a monodentate dppf ligand, which rapidly forms an equilibrium with the chelating dppf isomer complex [Pt(p-MeC 6 H 4 )(dppf)(ppy-κ 1 C)], B, in which ppy-κ 1 C is the deprotonated ppy ligand that is C-ligated with the dangling N atom. In the second step, A is reacted with the remaining second half of starting complex 1b to give the final Pt(II)-Pt(II) binuclear complex [Pt 2 (p-MeC 6 H 4 ) 2 (ppy) 2 (μ-dppf)], 2b. A competitive-consecutive second-order reaction mechanism was suggested for the reaction using chemometric studies, and the rate constants at 5 °C for first and second steps were estimated as k 2 = 10.7 ( 0.2 L mol -1 s -1 and k 2 0 = 0.68 ( 0.05 L mol -1 s -1 , respectively. When the starting complex [Pt(p-MeC 6 H 4 )(ppy)(SMe 2 )], 1b, was reacted with 1 equiv of dppf, similarly the complex A, in equilibrium with B, was formed first, with the rate constant at 5 °C being k 2 = 10.5 ( 0.5 L mol -1 s -1 , estimated using UV-visible spectroscopy. Subsequently, however, A and B would slowly and reversibly react with each other to form a new species, C, the structure of which, on the basis of 31 P and 195 Pt NMR spectra, was proposed to be [(p-MeC 6 H 4 )(ppy)Pt-(μ-dppf)Pt(p-MeC 6 H 4 )(ppy-κ 1 C)(dppf-κ 1 P)]; the same results were obtained when more than 1, e.g., 2, equiv of dppf was used, with a similar rate constant of k 2 = 10.6 ( 0.6 L mol -1 s -1 . The complexes 1b and 2b were shown to have some interesting photophysical properties as investigated by absorption and electroluminescence spectroscopies.

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