Kajian Teoritis Sifat Struktur dan Dinamika Ion Sc+ Singlet(1D) dan Triplet(3D) dalam Air, Amoniak Cair, dan Campuran Amoniak-air Menggunakan Simulasi Dinamika Molekuler AB Initio Mekanika Kuantum/Mekanika Molekuler

CRYS FAJAR PARTANA M.SI, Dr. rer.nat. Ria Armunanto, M.Si; Prof (ret) Dr. M. Utoro Yahya; Prof Dr. rer. nat. Harno Dwi Pranowo, M.S.

2015 | Disertasi | S3 Kimia

Sifat struktur dan dinamika solvasi ion Sc+ singlet (1D) dan triplet (3D) dalam air, amoniak cair, dan campuran amoniak-air telah dipelajari melalui simulasi dinamika molekuler mekanika kuantum/mekanika molekuler (DM MK/MM). Himpunan basis LANL2DZ ECP digunakan untuk ion Sc+ singlet (1D) dan ion triplet (3D), sedangkan DZP-DUNNING untuk atom N, O, dan H. Simulasi DM MK/MM ion Sc+ singlet (1D) dan triplet (3D) dalam air dilakukan dengan kondisi 1 ion Sc+ singlet (1D) dan triplet (3D) dalam 499 molekul air, dan suhu 298,16 K, sesuai dengan densitas air pada suhu tersebut 0,991 g cm-3. Simulasi DM MK/MM dalam amoniak cair dilakukan dengan kondisi 1 ion dalam 215 amoniak, suhu 235,26 K, sesuai dengan densitas amoniak cair pada suhu tersebut 0,690 g cm-3. Simulasi DM MK/MM dalam campuran amoniak-air dilakukan dengan kondisi 1 ion dalam campuran 92 molekul amoniak dan 407 molekul air, suhu 298,16 K, sesuai dengan densitas campuran amoniak-air pada suhu tersebut 0,927 g cm-3 dan konsentrasi 18,6 % amoniak. Simulasi DM MK/MM ion Sc+ singlet (1D) dan triplet (3D) dalam air, amoniak cair dan campuran amoniak-air dilakukan selama sekitar 25 ps. Struktur solvasi pertama dalam air terlihat ion Sc+ singlet (1D) mengikat 3 molekul air, sedangkan ion Sc+ triplet (3D) 2 molekul air. Kedua struktur solvasi kulit pertama tersebut bersifat rigid. Struktur solvasi kulit pertama ion Sc+ singlet (1D) dalam amoniak cair mengikat 3 molekul amoniak, sedangkan ion Sc+ triplet (3D) 2 molekul amoniak. Kedua struktur inipun bersifat rigid. Struktur solvasi kulit pertama ion Sc+ singlet (1D) dalam campuran amoniak-air terlihat membentuk kompleks [Sc(NH3)2(H2O)2]+ dan [Sc(NH3)2(H2O)3]+, sedangkan ion Sc+ triplet (3D) dalam campuran amoniak-air membentuk struktur kompleks [Sc(NH3)2(H2O)]+ dan [Sc(NH3)2(H2O)2]+. Struktur solvasi ion Sc+ singlet (1D) dan Sc+ triplet (3D) dengan amoniak bersifat rigid, sedangkan ion Sc+ singlet (1D) dan Sc+ triplet (3D) dengan air bersifat dinamis, karena selama simulasi terjadi pertukaran ligan.

THEORETICAL STUDY OF STRUCTURAL AND DYNAMICAL PROPERTIES OF SINGLET (1D) Sc+ AND TRIPLET (3D) IONS IN WATER, LIQUID AMMONIA, AND AMMONIA-WATER MIXTURE USING MOLECULAR DYNAMICS SIMULATION OF AB INITIO QUANTUM MECHANICS/MOLECULAR MECHANICS Structural and dynamical solvation properties of Sc+ singlet (1D) and Sc+ triplet (3D) ions in water, liquid ammonia and ammonia-water mixture have been studied using quantum mechanics/molecular mechanics molecular dynamics (QM/MM MD) simulation. The basis set Lanl2dz ecp was used for Sc+ singlet (1D) and Sc+ triplet (3D) ions, while DZP (Dunning) for N, O, and H atoms QM/MM MD simulation ion in water was conducted under one ion in 499 water molecule, at temperature 298.16 K, in accordance with density of water 0.9907 g cm-3. QM/MM MD simulation in liquid ammonia was performed under one ion in 215 ammonia at temperature 235.26 K, in accordance with the density of liquid ammonia 0.690 g cm-3. QM/MM MD simulation in ammonia-water mixture was conducted under one ion in mixture of 92 ammonia and 407 water molecules at temperature of 298.16 K, in accordance with the density of ammonia-water mixture 0.9270 g cm-3 and a concentration of 18.6% ammonia QM/MM MD simulation of Sc+ singlet (1D) and Sc+ triplet (3D) ions in water, liquid ammonia and ammonia-water mixture are performed about 25 ps obtaining the following results. First solvation structures of ion in water show Sc+ singlet (1D) binds 3 molecules of water, meanwhile the Sc+ triplet (3D) two water molecules. Both structures of the first solvation shells are rigids. The first solvation shell structures of ion in liquid ammonia show Sc+ singlet (1D) binds 3 molecules of ammonia, meanwhile Sc+ triplet (3D) two ammonia molecules. Both structures are also rigids. The first solvation shell structure of Sc+ singlet (1D) ion in ammonia-water mixture is composed [Sc(NH3)2(H2O)2]+ and [Sc(NH3)2(H2O)3]+ complex, meanwhile Sc+ triplet (3D) ion in ammonia-water mixture shows [Sc(NH3)2(H2O)]+ and [Sc(NH3)2(H2O)2]+ complex structure. Solvation structures of Sc+ singlet (1D) and Sc+ triplet (3D) ions with ammonia are rigid, meanwhile Sc+ singlet (1D) and Sc+ triplet (3D) ions with water are dynamic, due to the occurrence of ligand exchanges during simulation time.

Kata Kunci : simulasi DM MK/MM, Sc+ singlet (1D), Sc+ triplet (3D), air, amoniak