Department of Chemistry, The University of Burdwan, Golapbag, Burdwan-713 104, India.
J Phys Chem A. 2010 Jul 1;114(25):6776-86. doi: 10.1021/jp910809s.
The present paper reports, for the first time, supramolecular interaction of meso-octamethyl calix[4]pyrrole (1) with fullerenes C(60) and C(70) in solutions having varying polarity (e.g., toluene, 1,2-dichlorobenzene and benzonitrile and chloroform). The interaction is facilitated through charge transfer (CT) transition as evidenced from well-defined CT absorption bands in the visible region of absorption spectroscopy. Utilizing the CT transition energy for the complexes of 1 with various electron acceptors, we have determined the ionization potential of 1. Estimation of degrees of CT, oscillator, and transition dipole strengths suggest that the complexes are almost of neutral character in ground state. Higher magnitude of electronic coupling element value for the C(70)-1 complex compared to C(60)-1 indicates strong binding between C(70) and 1. Binding constants (K) of the fullerene-1 complexes have been determined from UV-vis investigations, which indicate high selectivity of 1 toward C(70). Extraordinary large K value of the C(70)-1 complex in chloroform medium (K approximately 1.43 x 10(6) dm(3) x mol(-1)) establishes that a polar environment facilitates such interaction. Both proton NMR and liquid IR studies provide very good support in favor of strong binding between C(70) and 1. (13)C NMR study proves that C(70) binds 1 with its equatorial belt, which substantiates the role of pi-pi interaction behind such strong interaction (i.e., high K value). Semiempirical theoretical calculations at the third parametric level (PM3) explore the stability difference between C(60)- and C(70)-1 complexes. PM3 calculations also reveal that approach of C(70) toward 1 is directed in side-on manner rather than in a conventional end-on alignment.
本文首次报道了介孔八甲基杯[4]吡咯（1）与富勒烯 C（60）和 C（70）在具有不同极性的溶液（例如甲苯、1,2-二氯苯和苯腈以及氯仿）中的超分子相互作用。通过电荷转移（CT）跃迁证实了这种相互作用，这可以从可见光谱区的吸收光谱中明显的 CT 吸收带得到证明。利用 1 与各种电子受体形成的 CT 跃迁能，我们确定了 1 的电离势。对 1 与各种电子受体形成的 CT 跃迁能的估算表明，在基态下，配合物具有几乎中性的特征。与 C（60）-1 相比，C（70）-1 复合物的电子耦合元素值的幅度更高，表明 C（70）与 1 之间具有较强的结合力。从 UV-vis 研究中确定了富勒烯-1 配合物的结合常数（K），这表明 1 对 C（70）具有高选择性。在氯仿介质中，C（70）-1 配合物的 K 值非常大（K 约为 1.43 x 10(6) dm(3) x mol(-1)），表明极性环境有利于这种相互作用。质子 NMR 和液体 IR 研究都非常支持 C（70）与 1 之间的强结合。13C NMR 研究证明 C（70）与 1 结合在其赤道带上，这证明了在这种强相互作用（即高 K 值）背后存在 pi-pi 相互作用的作用。第三参数水平（PM3）的半经验理论计算探索了 C（60）-和 C（70）-1 配合物之间的稳定性差异。PM3 计算还表明，C（70）向 1 的接近方式是侧向的，而不是传统的末端对齐方式。
