Molecular Electronic Resonance State Techniques

Author(s):  
W. H. McGregor ◽  
R. P. Howard
Author(s):  
LUTZ GALICH ◽  
HEINER HÜCKSTÄDT ◽  
HEINER HOMBORG

A vibrational resonance Raman effect of the totally symmetric Fe - F stretching mode at 453 cm−1is observed for high-spin tetra-n-butylammonium di(fluoro)tetraphenylporphyrinatoferrate(III). Typical A-term scattering with a high intensity overtone progression is proposed to be due to coincidence of the excitation energy with a ‘trip-sextet’ transition at 21 000 cm−1. The complex salt crystallizes as a dichloromethane solvate in the monoclinic space group P12/n1 (No. 13): a = 12.287(3) Å, b = 12.381(4) Å, c = 20.761(5) Å,β = 105.05(2)°,Z = 4. The iron atom is in the centre of the slightly distorted porphyrinate core. The Fe - F distance is 1.907(2) Å, the averaged Fe - Npdistance 2.072(2) Å. There is no hydrogen bonding of the floride ligand to the cation or solvate. Contrary to the high-spin difluoro complex, a molecular electronic resonance Raman effect is detected for low-spin pyridine(cyano)- and -(thiocyanato( N )tetraphenylporphyrinatoiron(III) at 550 and 561/578 cm−1respectively. This Γ7 g→Γ8 gtransition is a consequence of the spin-orbit splitting of the2T2 gground state of low-spin FeIIIassuming octahedral symmetry. B-term scattering is active by excitation with 476.5 nm, effectively enhancing the intensity of non-totally symmetric electronic and vibrational transitions.


Author(s):  
LUTZ GALICH ◽  
HEINER HÜCKSTÄDT ◽  
HEINER HOMBORG

The title complex salt has been isolated from a solution of chlorotetraphenylporphyrinatomanganese(III) and tetra(n-butyl)ammonium cyanide in dichloromethane. The complex salt crystallizes as a hydrate-dichloromethane solvate in the orthorhombic space group Pbca (no. 61) with cell parameters as follows: a = 21.491(5) Å, b = 21.706(5) Å, c = 28.489(5) Å, V = 13 290(5) Å3, Z = 8. The structure is that expected for a hexa-coordinated low-spin Mn ( III ) tetraphenylporphyrinate (magnetic moment: μ eff = 3.1 ± 0.2 μ B at 273 K). The Mn atom is in the centre of the slightly ruffled porphyrinato core. The Mn - C CN distance of 2.01(2)/2.02(2) Å and the Mn - N p distance, varying between 1.972(13) and 2.016(14) Å, are normal values. The Mn - C CN - N group is bent (171(2)/174(2) °). At low temperatures, a molecular electronic resonance Raman effect is detected at 198 and 344 cm−1. It is attributed to intraconfigurational transitions Γ 1g → Γ 4g and Γ 1g → Γ 3g Γ 5g , respectively, arising from the spin-orbit split 3 T 1g ground state of low-spin Mn ( III ), assuming pseudo-octahedral symmetry. Weak Q and intense B (Soret) transitions at 17 300 and 23 200 cm−1, respectively, as well as four weak trip–multiplet transitions are observed at 8650, 12 000, 14 900 and 19 900 cm−1.


1974 ◽  
Vol 10 (9) ◽  
pp. 748-749
Author(s):  
J. Biscar ◽  
N. Kollias ◽  
R. Burczyk

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