Transcript Slide 1
LORA Applied chemistry CHEM44415 * To explain how the mass susceptibility can be calculated.? * To explain how the molar susceptibility can be calculated from the mass susceptibility.? * To explain how the diamagnetic correction is carried out on xM to calculate xpara..? * To explain how the magnetic moment can be calculated.? * To predict the geometries and the spin state of the Co(II) complexes using magnetic moments.? Weight of empty tube, field off • 3.9506 g 1 2 Weight of empty tube, field on Weight of tube filled to line with water, field off • 3.9493 g 3 • 4.4319 g Standard Sample 1 Sample 2 4.6186 4.2371 4.2507 Weight of tube filled to line with solid, field off 4.2439 4 6 Weight of tube filled to line with solid, field on 4.6704 4.2899 4.2751 7 5 4.2825 (m)- (0.029 10-6 )V = (- ) Where m = tube filled with solid – empty tube = empty tube field on – empty tube field off = tube filled with solid, field on – tube filled with solid, field off V = (tube filled with water – empty tube) / density of water g of standard = 16.44E-6 cgs V= (3-1) / d (water) V= 0.4813 cm3(mL) = (2-1)= -0.0013 g Standard Sample = (5-4)= 0.0518 g = (7-6)= 0.0386 g m = (4-1)= 0.6680 g m = (6-1)= 0.2933 g we calculate (calibration constant) by using m, and Xg (mass susceptiblity )of the standard : (m)- (0.029 10-6 )V = (- ) X(g)= 16.44x10-6 cm3/g(emu/g) (m) (0.029 10 ) V 4 2.0655 10 6 (m)- (0.029 10-6 )V = (- ) By using the value of we calculate X(g) of the sample : ( ) (0.029 10 6 ) V g m 5 g 2.819 10 emu / g ( Molar suscebilit y ) : M g molar mass M (2.819 10 5 ) emu / g 361.362 g / mol 0.01018 emu / mol para = M - dia atom A(10-6) atom cm3/mol A(10-6) cm3/mol H -2.93 N -5.57 C( aliphatic) C( aromatic) S -6.00 N( aromatic) Co2+ -4.61 -6.24 -15.0 -12.00 Type of atom # of atoms xg Total XDIA Co2+ -12.8 x 10-6 -12.8 x 10-6 1 H 14 -2.9310-6 -4.102x10-5 C(aromatic) 10 -6.24 10-6 -6.24x10-5 C(aliphatic) 4 -6.00 10-6 -2.40x10-5 N(aromatic) 2 -4.61 10-6 -9.22x10-6 N (aliphatic) 2 -5.57 10-6 -1.114x10-5 S 2 -15.00 10-6 -3.00x10-5 Total= -1.9058x10-4 cm3/mol. AND Remember that this unit = emu/mol x para xM xDIA x para 0.01018 1.9058 10 4 emu / mol 0.01037 emu / mol ( BM 2 / K eff 2.828 T X para eff 2.828 295 K 0.01037 BM 2 / K eff 4.95 BM From this value. How can you determine the geometry and the spin state of the complex..? Co2+ (d7) Co2+ (d7) High Spin Low Spin eg eg t2g t2g n 1, S 1 / 2, L 5 n 3, S 3 / 2 , L 3 us 4S S 1 u s 4S S 1 1/ 2 1/ 2 1.73BM 3.87 BM 1 u S L 2 S S 1 LL 1 4 5.19 1/ 2 1 uS L 2 S S 1 LL 1 4 6.16 BM 1/ 2 Tetrahedral Co2+ (d7) only High Spin t2 e n 3, S 3 / 2 , L 3 u s 4S S 1 1/ 2 3.87 BM 1 u S L 2 S S 1 LL 1 4 5.19 1/ 2 Tetrahedral geometry Complexes Co(py)2Cl2 Co(py)2I2 Color (solid) Blue Blue μeff (B.M) 4.42 4.47 Co(Py)2Br2 Co(2-Me-py)2 (Cl)2 Blue Blue 4.50 4.47 Co(2-Me-py)2 (NCS)2 Blue 4.30 Co(3-Me-py)2Cl2 Blue 4.49 Co(3-Me-py)2Br2 Blue 4.48 Co(3-Me-py)2(NCS)2 Blue 4.30 Complexes Color (solid) μeff (B.M) Co(4-Me-py)2Br2 Blue 4.41 Co(4-Me-py)2(NCS)2 Blue 4.30 Co(3-Et-py)2Br2 Blue 4.70 Co(3-Et-py)2(NCS)2 Blue 4.46 Co(4-Et-py)2Br2 blue 4.45 The magnetic moment of tetrahedral geometry is in range(4.30 – 4.74 B.M.) and absorb light strongly at range (580-780) nm. Octahedral geometry Complexes Co(py)4Cl2 Co(Py)4(NCS)2 Color (solid) Pink Purple-red μeff (B.M) 5.15 5.10 Co(3-Me-py)4Cl2 Co(3-Me-py)4Br2 Pink Pink 4.94 5.07 Co(3-Me-py)4(NCS)2 Pink 5.03 Co(4-Me-py)4(NCS)2 Lilac 4.92 Co(3-Et-py)4Br2 Pink 5.02 Co(3-Et-py)4(NCS)2 lilac 5.15 The magnetic moment of octahedral geometry is in range(4.90 – 5.40 B.M.) and absorb light weakly in the range (640-600 nm) High λ Low ∆0 HS. ueff= 4.95 BM Tetrahedral (4.30-4.74 ) BM 1.Magnetic moments are used to determine the spin state (high spin or low spin). 2.Octahdral complexes can be either high spin or low spin. 3.Tetrahedral complexes can only be high spin. 4.Experimental magnetic moments for Co(II) Complexes are always higher than the spin-only magnetic moments because of the significant Orbital contribution . 5.The magnitude of the orbital contribution differ for tetrahedral and octahedral ,it is greater for octahedral than for tetrahedral. Therefore ,we can distinguish between tetrahedral and octahedral. Tetrahedral; 4.30 – 4.72 B.M. Octahedral; 4.90 – 5.40 B.M. 2.