Abstract:The iron(n) complex [Fe(bpp),]-(CF3S03),.H,0 (bpp = 2,6-bis(pyrazolyl-3-y1)pyridine) shows a thermal spin transition associated with a hysteresis of approximately 140 K width. The transition temperatures TI,, (where the fraction of HS species y H S = 0.5) are 147 K and ~2 8 5 K in the cooling and heating directions, respectively. The compound shows the LIESST and reverse-LIESST effects at low temperatures. The relaxation of the metastable HS states generated by LIESST was observed quantitatively at temperatures between 77.5 and 85 K by Mossbauer spectroscopy. Metastable HS states can also be generated by rapid cooling of the sample. The relaxation of the

Penelitian ini bertujuan untuk: (1) mengembangkan multimedia berbasis masalah dengan materi redoks, (2) menganalisis kualitas multimedia berbasis masalah, serta (3) menguji keefektifan multimedia berbasis masalah dalam meningkatkan motivasi belajar dan kemampuan berpikir kritis peserta didik. Penelitian ini termasuk dalam penelitian dan pengembangan berdasarkan model Borg & Gall. Subjek uji coba dalam penelitian ini meliputi peserta didik kelas X SMA Negeri 6 Yogyakarta. Data dikumpulkan melalui angket untuk validasi media, lembar observasi keterlaksanaan pembelajaran, lembar observasi motivasi belajar, angket motivasi belajar, dan tes kemampuan berpikir kritis. Hasil penelitian menunjukkan bahwa (1) pengembangan multimedia berbasis masalah materi redoks dilaksanakan sesuai dengan prosedur pengembangan, (2) secara umum kualitas multimedia berbasis masalah termasuk dalam kategori sangat baik, dan (3) multimedia berbasis masalah efektif untuk meningkatkan motivasi belajar dan kemampuan berpikir kritis peserta didik pada pembelajaran materi redoks. Kata kunci: multimedia berbasis masalah, motivasi belajar, kemampuan berpikir kritis.   DEVELOPING MULTIMEDIA BASED ON PROBLEM TO INCREASE STUDENT’S LEARNING MOTIVATION AND CRITICAL THINKING SKILL Abstract The aims of this research are (1) developing the multimedia based on problem in redox’s chapter, (2) analysing the quality of multimedia based on problem, and (3) testing the effectiveness of multimedia based on problem in increasing student’s learning motivation and critical thinking skill. This research used Borg & Gall research and development’s model. The subject of the research is the grade X students of SMA Negeri 6 Yogyakarta. The data were collected by using media validation’s questionnaire, learning process observation sheet, learning motivation’s questionnaire and obser-vation sheet, and critical thinking skill’s test. The results of the research show that (1) the development of multimedia based on problem in redox’s chapter is done based on the development procedure, (2) generally, the quality of multimedia which has been developed can be categorized as very good; and (3) the multimedia based on problem is effective to increase student’s learning motivation and critical thinking skill in redox’s chapter. Keywords: multimedia based on problem, learning motivation, critical thinking skill

The magnetic and Mossbauer spectral properties of hydrated and anhydrous complex salts [Fe( bpp )2] X2, where bpp = [2,6-bis(pyrazol-3-yl)pyridine] and X = PF6, BF4, Br, I, NO3, are indicative of a temperature-induced singlet (1A1) ↔ quintet (5T2) transition in the complex cation. The nature of the transition depends on the anion and the degree of hydration. The transition is displaced to lower temperatures in the anhydrous species and for the hydrated is only partial above room temperature. The transition in the hydrated hexafluorophosphate salt occurs in two steps, and that in the anhydrous hexafluorophosphate is incomplete, a high residual fraction of quintet state species being retained below the transition temperature. For the anhydrous complexes the transition is discontinuous and that in the complex iodide is associated with a narrow thermal hysteresis with transition temperatures Tc ↓ = 203 K and Tc ↑ = 205 K. The structures of [Fe( bpp )2]I2.4H2O and [Fe( bpp )2][BF4]2.3H2O have been determined at 298 K. Both complex salts are essentially low spin at this temperature and have an average Fe-N distance of 1.95 Ǻ. The structures reveal in both instances an extended hydrogen-bonded network involving the uncoordinated >NH groups of the ligands, the anions and lattice water. It is suggested that it is this bonding which is responsible for the favouring of the singlet state in the hydrated salts. Bis [2,6-bis(pyrazol-3-yl)pyridine]iron(II) diiodide tetrahydrate : triclinic, space group Pī , a 8.276(8), b 8.305(7), c 21.941(27) Ǻ, α 98.11(5), β 90.08(6), γ 90.82(6)°, Z 2. Bis [2,6-bis(pyrazol-3-yl)pyridine]iron(II) bis ( tetrafluoroborate ) trihydrate : monoclinic, space group C2/c, a 31.222(15), b 14.456(3), c 12.907(5) Ǻ, β 99.40(2)°, Z 8.

The 3D visualization program paves the way for the development of virtual reality. This study produces a 3D visualization program in virtual reality to increase high school students' critical thinking skills and scientific attitude. The Research and Development (R&D) method was based on the ADDIE modelanalysis, design, develop, implement, and evaluate with quasi experimentalposttest design. The data of students' scientific attitude was collected through questionnaire adapted from several books and jounals, and those of the students' critical thinking skills was collected through chemical bonding test. A total of 96 grade 10th students were cluster randomly selected from senior high school in Gunungkidul Regency, Yogyakarta, Indonesia. The samples were set into three different classes, namely Class CG using a wet laboratory, Class EG-1 using a virtual reality laboratory integrated hybrid learning, and Class EG-2 using both of them. Based on the MANOVA test, it was found that students who used 3D visualization had better results in critical thinking skills and scientific attitudes.

Iron(II) and nickel(II) [MN6]X2 type complexes have been prepared from 2-(pyrazol-1-yl]pyridine (1pp), 2-(pyrazol-1-yl) imidazoline (pi), 2- (pyrazol-3-yl)pyridine (3pp) and 2,6-bis(pyrazol-3-yl)pyridine ( bpp ). Variable-temperature magnetic and Mossbauer spectral studies establish that [Fe(1pp)3]X2 is low spin and [Fe(pi)3]X2 is high spin over an extended temperature range, while both [Fe(3pp)3]X2 and [Fe( bpp )2]X2 undergo temperature-induced low-spin ↔ high-spin transitions. The nature of the transition depends on the extent of hydration and for salts of both cations the singlet state is generally stabilized as the extent of hydration increases. Hydrogen bonding effects are believed to be responsible for this. For anhydrous [Fe( bpp )2] [BF4]2 the transition is discontinuous and associated with hysteresis with Tc ↓ 173 K for decreasing temperature and Tc ↑ 183 K for increasing temperatures. The transition to the singlet state species is complete at low temperatures provided that the cooling rate is relatively slow. Rapid cooling to 77 K results in the trapping of a fraction of metastable quintet state species. For all other species containing either [Fe(3pp)3]2+ or [Fe( bpp )2]2+ the spin transition is continuous. Spectral data for [NiN6]X2 complexes establish an order of field strengths for the ligands pi < 3pp < 1pp < bpp , which, for the bidentate species only, is consistent with the observed electronic properties of the corresponding [FeN6]X2 complexes.