KONFORMASI KOMPLEKS [Zn2+.Bz12C4] TERSUBSTITUSI DALAM SISTEM MIKROSOLVASI BERDASARKAN METODE MP2

Mega Drupadi, S.Si, Prof. Dr. Harno Dwi Pranowo, M.Si.

2012 | Tesis | S2 Ilmu Kimia

Selektifitas eter mahkota benzo‐12‐mahkota‐4 (Bz12C4) dalam mengikat kation Zn2+ telah dianalisis berdasarkan perhitungan kimia komputasi menggunakan metode Post‐SCF/MP2 pada tingkat himpunan basis LanL2MB. Pengaruh subsituen – CH=CH2, ‐OH, ‐COOH, dan –Br terhadap Bz12C4, interaksi antara Bz12C4 dengan Zn2+, serta interaksi antara kompleks [Zn2+.Bz12C4] dengan molekul air dikaji menggunakan perhitungan kimia komputasi. Optimasi geometri dilakukan terhadap eter mahkota, kompleks eter mahkota‐kation, dan kompleks eter mahkota‐kation dalam sistem mikrosolvasi. Interaksi antara eter mahkota‐kation dalam sistem mikrosolvasi dikaji dengan melakukan analisis parameter struktur eter mahkota, muatan atom, dan energi interaksi. Selektifitas eter mahkota dalam mengikat kation ditentukan oleh kesesuaian antara diameter kation dengan kavitas eter mahkota. Substituen yang terikat pada benzena yang dapat meningkatkan kesimetrisan kompleks eter mahkota‐kation dapat meningkatkan selektifitas eter mahkota dalam mengikat kation. Gugus pendorong elektron dapat meningkatkan kemampuan eter mahkota dalam mengikat kation melalui efek induksi, sedangkan gugus penarik elekron dapat menurunkan kemampuan eter mahkota dalam mengikat kation. Hanya penambahan satu molekul air yang dapat dimodelkan dalam sistem mikrosolvasi. Konformasi kompleks [Zn2+.Bz12C4] dalam sistem mikrosolvasi berdasarkan metode MP2 memberikan hasil ion Zn2+ tidak terletak satu bidang dengan atom‐atom oksigen pada 12C4.

Selectivity of benzo‐12‐crown‐4 (Bz12C4) to bind a Zn2+ cation was analyzed based on computational chemistry calculations using Post‐SCF/MP2 method using LanL2MB as a basis set. The substituent effects of –CH=CH2, ‐OH, ‐COOH, and –Br on Bz12C4, interaction between substituted Bz12C4 with Zn2+ cation, and interaction between [Zn2+. Bz12C4] complexes with water were evaluated using computational chemistry calculations. The structure of crown ether, crown ether‐cation complex, and crown ether‐cation complexes in the microsolvation system has been optimized. Interaction of the crown ether‐cation and microsolvation system was discussed in term of the structure parameter of crown ether, atomic charges, and energy interaction. Selectivity of the crown ether to bind cation depends on the compatibility of the diameter cation of cation and cavity of crown ether. Any substituent on the benzene in crown ether which supports the symmetrical form of the crown ethermetal cation complexes would increase the selectivity of the crown ether to bind the cation. The electron donating groups would increase the capability of crown ether to bind cation by means of induction effect, while electron withdrawing groups reduce the ability of crown ether to bind cation. There was just one addition of water molecule that can be used to modeling in the microsolvation system. The MP2 method gave [Zn2+.Bz12C4] complexes unplanar conformation between Zn2+ and the oxygens on the 12C4.

Kata Kunci : Benzo‐12‐mahkota‐4, Zn2+ , Post‐SCF, LanL2MB, mikrosolvasi