Kristian H. Sugiyarto

Electronic and Structural Properties of the Spin Crossover Systems Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Thiocyanate and Selenocyanate

Essentially high-spin [Fe(bpp)2][NCS]2·2H2O and [Fe(bpp)2][NCSe]2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) were isolated from an aqueous reaction mixture. Both salts undergo an abrupt transition to low spin below room temperature, that for the thiocyanate occurring in two steps and the high-spin AE low-spin AE high-spin cycle being accompanied by hysteresis in both steps. Recrystallization of the salts from nitromethane yielded a mixture from which bright yellow crystals were separated for structure determination. In addition, from the recrystallized selenocyanate, deep red-brown crystals of composition [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2 were obtained. Recrystallized [Fe(bpp)2][NCS]2·2H2O and [Fe(bpp)2][NCSe]2 were identified as high spin with average Fe–N distances of 2.16 and 2.17 A, respectively. In the unit cell of [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2, there are four independent iron atoms, three identified as low spin and the fourth as high spin. All salts crystallize in a layer-type array involving edge-to-face and face-to-face aryl–aryl-type interactions. Hydrogen bonding between pyrazole >NH groups, anions and solvate molecules is observed. The structure of the uncoordinated ligand was also determined, the molecule being found in a planar arrangement with thecis–cis configuration for the pyrazolyl groups relative to the central pyridyl and the >NH group being at the N 2 atom. Hydrogen bonding involving the >NH groups leads to stepped stacks of molecules. The principal difference in the geometry of coordinated and free bpp molecules is a contraction in the angles about the interannular bridges in the chelate rings. [Fe(bpp)2][NCS]2·2H2O: triclinic, space group P1–, a 8.302(6), b 8.446(6), c 21.531(13) A, a 78.78(5), b 82.80(5), g 89.85(4)˚, Z 2. [Fe(bpp)2][NCSe]2: triclinic, space group P1–, a 8.354(4), b 8.409(4), c 19.918(9) A, a 87.02(3), b 83.15(3), g 88.86(3)˚, Z 2. [Fe(bpp)2][NCSe]2·H2O·0.25 CH3NO2: monoclinic, space group Pn, a 16.425(12), b 20.774(9), c 16.933(14) A, b 90.91(4)˚, Z 8. Uncoordinated bpp: orthorhombic, space group Pna21, a 8.075(3), b 22.479(9), c 5.525(1) A, b Z 4.

Lattice trapping of metastable quintet state bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) bis(tetrafluoroborate), a spin crossover system, and kinetics of the quintet-singlet transformation

Abstract The 5 T 2 ⇌ 1 A 1 spin transition in [Fe(bpp) 2 ][BF 4 ] 2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) is abrupt and complete and shows hysteresis with the transition temperatures T c ↓ = 173 K and T c ↑ = 183 K. Rapid cooling of the sample causes the freezing-in of metastable quintet state species at low temperatures. Relaxation of the metastable quintet to singlet state species within the range 99–114 K follows simple first-order kinetics with an activation energy E a = 19.5 kJ mol −1 .

The measurement of self-efficacy in the use of VICH-LAB in electrochemistry

A virtual laboratory known as VICH-LAB (Virtual Chemistry Laboratory) has been developed in hybrid learning. This VICH-LAB was used in electrochemistry classes involving much practice work with various tools and materials. VICH-LAB contains a MSDS (Material Safety Data Sheet), tools introduction, interactive practicum, and assignments. The aim of this study was to measure self-efficacy in the use of VICH-LAB. The design of this research was quasi-experimental with a post-test design. Differences among 3 classes with different treatments was observed. The first class used a wet laboratory, the second class used a virtual laboratory integrated hybrid learning approach, and a third class used both of them. All three classes took place during the same academic term and had the same teachers. The variable measured in the three classes was self-efficacy, measured with a questionnaire consisting of 22 items. Self-efficacy scores were significantly different between the class using a wet laboratory and the class that was using the wet laboratory and VICH-LAB as a supplement.A virtual laboratory known as VICH-LAB (Virtual Chemistry Laboratory) has been developed in hybrid learning. This VICH-LAB was used in electrochemistry classes involving much practice work with various tools and materials. VICH-LAB contains a MSDS (Material Safety Data Sheet), tools introduction, interactive practicum, and assignments. The aim of this study was to measure self-efficacy in the use of VICH-LAB. The design of this research was quasi-experimental with a post-test design. Differences among 3 classes with different treatments was observed. The first class used a wet laboratory, the second class used a virtual laboratory integrated hybrid learning approach, and a third class used both of them. All three classes took place during the same academic term and had the same teachers. The variable measured in the three classes was self-efficacy, measured with a questionnaire consisting of 22 items. Self-efficacy scores were significantly different between the class using a wet laboratory and the class ...

Collaboration of chemistry instructional games and group investigation (Gi) model to improve learning outcome in high school students

The aims of this research are to: (1) develop chemistry instructional games on reaction rate matter; and (2) reveal the collaboration of chemistry instructional games and group investigation model to improvement learning outcome in high school student. This study is research and development (RD and (2) the...

The effect of the use of android-based application in learning together to improve students’ academic performance

Poor achievement of students’ performance on Chemistry may result from unfavourable learning processes. Therefore, innovation on learning process must be created. Regarding fast development of mobile technology, learning process cannot ignore the crucial role of the technology. This research and development (R&D) studies was done to develop android based application and to study the effect of its integration in Learning together (LT) into the improvement of students’ learning creativity and cognitive achievement. The development of the application was carried out by adapting Borg & Gall and Dick & Carey model. The developed-product was reviewed by chemist, learning media practitioners, peer reviewers, and educators. After the revision based on the reviews, the application was used in the LT model on the topic of Stoichiometry in a senior high school. The instruments were questionnaires to get comments and suggestion from the reviewers about the application, and the another questionnaire was to collect the...