Penerapan Model Pembelajaran Atraktif Berbasis Multiple Intelligences Tentang Pemantulan Cahaya pada Cermin

Penelitian ini bertujuan untuk mengetahui efektivitas penerapan model pembelajaran atraktif berbasis multiple intelligences dalam meremediasi miskonsepsi siswa tentang pemantulan cahaya pada cermin. Pada penelitian ini digunakan bentuk pre-eksperimental design dengan rancangan one group pretest-post test design. Alat pengumpulan data berupa tes pilihan ganda dengan reasoning. Hasil validitas sebesar 4,08 dan reliabilitas 0,537. Siswa dibagi menjadi lima kelompok kecerdasan, yaitu kelompok linguistic intelligence, mathematical-logical intelligence, visual-spatial intelligence, bodily-khinestetic intelligence, dan musical intelligence. Siswa membahas konsep fisika sesuai kelompok kecerdasannya dalam bentuk pembuatan pantun-puisi, teka-teki silang, menggambar kreatif, drama, dan mengarang lirik lagu. Efektivitas penerapan model pembelajaran multiple intelligences menggunakan persamaan effect size. Ditemukan bahwa skor effect size masing-masing kelompok berkategori tinggi sebesar 5,76; 3,76; 4,60; 1,70; dan 1,34. Penerapan model pembelajaran atraktif berbasis multiple intelligences efektif dalam meremediasi miskonsepsi siswa. Penelitian ini diharapkan dapat digunakan pada materi fisika dan sekolah lainnya

Dinitrogen and Acetylide Complexes of Low-Valent Chromium

Reaction of trans-(dmpe)2CrCl2 (dmpe = 1,2-bis(dimethylphosphino)ethane) with one equivalent of LiCCSiMe3 and one equivalent of nBuLi in THF under a dinitrogen atmosphere affords dark orange trans,trans-[(Me3SiCC)(dmpe)2Cr]2(µ-N2)·hexane (1). Under similar conditions but in the absence of acteylide ligand, the reaction of trans-(dmpe)2CrCl2 with 2 equivalents of nBuLi yields the previously characterized complex trans-(dmpe)2Cr(N2)2 (2), while the reaction of trans-(dmpe)2CrCl2 with 2 equivalents of LiCCSiMe3 in THF yields trans-(dmpe)2Cr(CCSiMe3)2 (3). Compound 3 can also be synthesized by irradiating a mixture of trans-(dmpe)2CrMe2 and HCCSiMe3 or by reduction of HCCSiMe3 with compound 2. The magnetic properties, electrochemistry, and crystal structure of trans,trans-[(Me3SiCC)(dmpe)2Cr]2(µ-N2) are consistent with the complex containing two CrI ions bridged by a neutral N2 moiety, with a 1.178(10) Å NN bond distance. For complex 1 redox processes centered at E1/2 = –1.69 V (ΔEp = 185 mV) and –1.43 V (ΔEp = 182 mV) versus Fe(Cp)2/Fe(Cp)2+ are assigned to the CrICrI/CrICrII and CrICrII/CrIICrII couples, respectively. For trans-(dmpe)2Cr(CCSiMe3)2 a reversible couple assigned as the CrII/III couple was observed at –1.59 V (ΔEp = 242 mV) versus Fe(Cp)2/Fe(Cp)2+. The dinuclear Cr(I)−dinitrogen complex 1 has a room temperature magnetic moment of 2.77 µB while compound 3 displays a moment of 2.55 µB. Density-functional theory calculations performed on a model compound of 1, namely, trans,trans-[(HCC)(dpe)2Cr]2(µ-N2) (dpe = diphospinoethane), indicate that oxidation of the molecule should result in weakening of the dinitrogen triple bond

Countercations Direct One- or Two-Electron Oxidation of an Al(III) Complex and Al(III)–Oxo Intermediates Activate C–H Bonds

Hydrogen abstraction by aluminum(III)–oxo intermediates via reaction pathways reminiscent of late transition metal chemistry has been observed. Oxidation of M+[(IP2–)2Al]− (IP = iminopyridine, M = Na, Bu4N) yielded [Na(THF)(DME)][(IP–)(IP2–)Al(OH)] (3) or [(IP–)2Al(OH)] (4), via O-atom transfer and subsequent C–H activation or proton abstraction, respectively

Synthesis and Alkali Metal Ion-Binding Properties of a Chromium(III) Triacetylide Complex

A simple triacetylide complex of chromium(III) is synthesized for use as a potential precursor to metal-dicarbide clusters. Reaction of Me3SiCCLi with [(Me3tacn)Cr(CF3SO3)3] (Me3tacn = N,N‘,N‘‘-trimethyl-1,4,7-triazacyclononane) in THF generates [(Me3tacn)Cr(CCSiMe3)3], which subsequently reacts with Bu4NF to supply [(Me3tacn)Cr(CCH)3] as an air-stable orange solid. The crystal structure of this unprecedented triacetylide complex reveals octahedral coordination of the chromium center, with linear Cr−C⋮C bond angles and C⋮C bond distances essentially identical to the corresponding distance in acetylene. Crystallization of the complex from a DMF solution containing K(CF3SO3) leads to the sandwich complex {[(Me3tacn)Cr(CCH)3]2K}+, in which the K+ ion is coordinated in a side-on fashion by each of the six C⋮C units. With the larger Cs+ cation, a triangular {[(Me3tacn)Cr(CCH)3]3Cs}+ complex is instead observed. The magnetic properties of these alkali metal complexes are indicative of weak antiferromagnetic exchange between CrIII centers, with J = −0.8 and −0.3 cm-1, respectively

A Sterically Demanding Iminopyridine Ligand Affords Redox-Active Complexes of Aluminum(III) and Gallium(III)

The combination of an electrophilic metal center with a redox active ligand set has the potential to provide reactivity unique from transition metal redox chemistry. In this report, substituted iminopyridine complexes containing monoanionic and dianionic MeIPMes ligands have been characterized structurally and electronically. Green (MeIPMes–)­AlCl2 (1), (MeIPMes–)­AlMe2 (2), and (MeIPMes–)­GaCl2 (5) have a doublet spin state which results from the anion radical form of MeIPMes. Purple (MeIPMes2–)­AlCl­(OEt2) (3), (MeIPMes2–)­AlMe­(OEt2) (4), and (MeIPMes2–)­GaCl­(OEt2) (6) are each diamagnetic. We have also investigated the solvent dependence of the decomposition of the MeIPMes anion radical. Complexes 1 and 2 can be obtained from benzene and hexanes whereas the use of ether solvents results in the formation of undesirable (CH2IPMes–)­AlCl2 (1a) and (CH2IPMes–)­AlCl2 (2a) formed by loss of a hydrogen atom from the MeIPMes– ligand. Electrochemical measurements indicate that 1, 2, and 5 are redox active

Countercations Direct One- or Two-Electron Oxidation of an Al(III) Complex and Al(III)–Oxo Intermediates Activate C–H Bonds

Hydrogen abstraction by aluminum(III)–oxo intermediates via reaction pathways reminiscent of late transition metal chemistry has been observed. Oxidation of M+[(IP2–)2Al]− (IP = iminopyridine, M = Na, Bu4N) yielded [Na(THF)(DME)][(IP–)(IP2–)Al(OH)] (3) or [(IP–)2Al(OH)] (4), via O-atom transfer and subsequent C–H activation or proton abstraction, respectively

Dimanganese and Diiron Complexes of a Binucleating Cyclam Ligand: Four-Electron, Reversible Oxidation Chemistry at High Potentials

The reaction of a binucleating biscyclam ligand cyclam2iPrO [where cyclam2iPrO = (1,3-bis[1,4,8,11-tetraazacyclododecane]-2-hydroxypropane] with Mn(CF3SO3)2 or Fe(CF3SO3)2·2MeCN gives [(cyclam2iPrO)Mn2(μ-CF3SO3)](CF3SO3)2 (4) and [(cyclam2iPrO)Fe2(μ-CF3SO3)](CF3SO3)2 (6), respectively. [(cyclam2iPrO)Mn2(μ-N3)](CF3SO3)2 (5) is obtained by the reaction of 4 with NaN3. Single-crystal X-ray structural characterization indicates that in each of the bimetallic complexes the two metal centers are facially coordinated by a cyclam ligand and bridged by the isopropoxide linker of the ligand in addition to a triflate counteranion. Upon replacement of the triflate bridge with the single-atom bridge of an end-bound azide ligand in 5, the MnMn distance decreases by 0.38 Å. All of the complexes are high-spin and colorless and were characterized by magnetic susceptibility measurements, electron paramagnetic resonance spectroscopy, and electrochemical methods. Magnetic susceptibility measurements indicate that 4 and 6 are weakly antiferromagnetically coupled while 5 is weakly ferromagnetically coupled. Cyclic voltammetry measurements indicate that the hard donor amine ligands impart high oxidation potentials to the metal centers and that four-electron redox activity can be accessed with a narrow potential range of 0.72 V. Upon inclusion of water in the cyclic voltammetry experiment, the oxidative waves shift to higher potentials, which is consistent with water binding the manganese centers. The diiron complex 6 displays four one-electron redox couples, of which the final two are irreversible. Inclusion of water in the cyclic voltammetry measurement for compound 6 resulted in two sets of shifted peaks, which suggests that two molecules of water bind the diiron core. In accordance with the observed reversibility of the electrochemical results, the dimanganese complex is more efficient than the diiron complex for mediating O-atom transfer to organic substrates and is an excellent hydrogen peroxide disproportionation catalyst, with the reaction proceeding for over 20 000 turnovers

Dimanganese and Diiron Complexes of a Binucleating Cyclam Ligand: Four-Electron, Reversible Oxidation Chemistry at High Potentials

The reaction of a binucleating biscyclam ligand cyclam2iPrO [where cyclam2iPrO = (1,3-bis[1,4,8,11-tetraazacyclododecane]-2-hydroxypropane] with Mn(CF3SO3)2 or Fe(CF3SO3)2·2MeCN gives [(cyclam2iPrO)Mn2(μ-CF3SO3)](CF3SO3)2 (4) and [(cyclam2iPrO)Fe2(μ-CF3SO3)](CF3SO3)2 (6), respectively. [(cyclam2iPrO)Mn2(μ-N3)](CF3SO3)2 (5) is obtained by the reaction of 4 with NaN3. Single-crystal X-ray structural characterization indicates that in each of the bimetallic complexes the two metal centers are facially coordinated by a cyclam ligand and bridged by the isopropoxide linker of the ligand in addition to a triflate counteranion. Upon replacement of the triflate bridge with the single-atom bridge of an end-bound azide ligand in 5, the MnMn distance decreases by 0.38 Å. All of the complexes are high-spin and colorless and were characterized by magnetic susceptibility measurements, electron paramagnetic resonance spectroscopy, and electrochemical methods. Magnetic susceptibility measurements indicate that 4 and 6 are weakly antiferromagnetically coupled while 5 is weakly ferromagnetically coupled. Cyclic voltammetry measurements indicate that the hard donor amine ligands impart high oxidation potentials to the metal centers and that four-electron redox activity can be accessed with a narrow potential range of 0.72 V. Upon inclusion of water in the cyclic voltammetry experiment, the oxidative waves shift to higher potentials, which is consistent with water binding the manganese centers. The diiron complex 6 displays four one-electron redox couples, of which the final two are irreversible. Inclusion of water in the cyclic voltammetry measurement for compound 6 resulted in two sets of shifted peaks, which suggests that two molecules of water bind the diiron core. In accordance with the observed reversibility of the electrochemical results, the dimanganese complex is more efficient than the diiron complex for mediating O-atom transfer to organic substrates and is an excellent hydrogen peroxide disproportionation catalyst, with the reaction proceeding for over 20 000 turnovers

Dinitrogen and Acetylide Complexes of Low-Valent Chromium

Reaction of trans-(dmpe)2CrCl2 (dmpe = 1,2-bis(dimethylphosphino)ethane) with one equivalent of LiCCSiMe3 and one equivalent of nBuLi in THF under a dinitrogen atmosphere affords dark orange trans,trans-[(Me3SiCC)(dmpe)2Cr]2(µ-N2)·hexane (1). Under similar conditions but in the absence of acteylide ligand, the reaction of trans-(dmpe)2CrCl2 with 2 equivalents of nBuLi yields the previously characterized complex trans-(dmpe)2Cr(N2)2 (2), while the reaction of trans-(dmpe)2CrCl2 with 2 equivalents of LiCCSiMe3 in THF yields trans-(dmpe)2Cr(CCSiMe3)2 (3). Compound 3 can also be synthesized by irradiating a mixture of trans-(dmpe)2CrMe2 and HCCSiMe3 or by reduction of HCCSiMe3 with compound 2. The magnetic properties, electrochemistry, and crystal structure of trans,trans-[(Me3SiCC)(dmpe)2Cr]2(µ-N2) are consistent with the complex containing two CrI ions bridged by a neutral N2 moiety, with a 1.178(10) Å NN bond distance. For complex 1 redox processes centered at E1/2 = –1.69 V (ΔEp = 185 mV) and –1.43 V (ΔEp = 182 mV) versus Fe(Cp)2/Fe(Cp)2+ are assigned to the CrICrI/CrICrII and CrICrII/CrIICrII couples, respectively. For trans-(dmpe)2Cr(CCSiMe3)2 a reversible couple assigned as the CrII/III couple was observed at –1.59 V (ΔEp = 242 mV) versus Fe(Cp)2/Fe(Cp)2+. The dinuclear Cr(I)−dinitrogen complex 1 has a room temperature magnetic moment of 2.77 µB while compound 3 displays a moment of 2.55 µB. Density-functional theory calculations performed on a model compound of 1, namely, trans,trans-[(HCC)(dpe)2Cr]2(µ-N2) (dpe = diphospinoethane), indicate that oxidation of the molecule should result in weakening of the dinitrogen triple bond