Far-i.r. and Raman spectra of (RNC)6Mn+ compounds (R = CH3, C6H5, 4-Cl—C6H4)

Manganese(I) Complex with Monodentate Arylisocyanide Ligands Shows Photodissociation Instead of Luminescence

“…Infrared spectra of the complex and the free ligand were measured in the range of 400–3500 cm –1 (Figure ). The CN stretching frequency (υ­(C  N)) of isocyanides is usually strongly influenced by the metal coordination, ,,,,− and this is also the case here. In the IR spectrum of the free ligand, υ­(CN) is observed at 2116 cm –1 , which is nearly the same for the analogous W-complex (2115 cm –1 ), whereas in the complex [Mn­(CNdippPh OMe2 ) 6 ]­PF 6 , it is shifted to 2070 cm –1 , due to π-backbonding from the metal center to the π* antibonding orbital of the isocyanide moiety.…”

“…A complex with O h symmetry should furthermore exhibit one Raman-active (triply degenerate T 2 g ), one forbidden (triply degenerate T 2 u ), and one IR-active (triply degenerate T 1 u ) metal–ligand bending mode (δ­(Mn–CN) as well as for δ­(C–Mn–C)). ,, The calculations reveal between 599 and 618 cm –1 six-core vibration bending modes in x , y , and z directions with dominant Mn motions (Table ). Specifically, these modes are at 599.57, 601.19, 608.21, 610.13, 613.87, and 618.43 cm –1 .…”

“…For an ideal octahedral complex of the type [Mn–(C–N–C­(Ar)) 6 ], six IR-active T 1 u modes are expected (υ­(CN), υ­(Mn–C), υ­(N-C­(Ar)), δ­(Mn–CN), δ­(C–Mn–C), and δ­(CN-C­(Ar))) . The infrared spectrum was analyzed only in terms of [Mn­(−CN)] core vibrations (Table ).…”

“…The core vibrations of [Mn­(CNdippPh OMe2 ) 6 ] + were obtained from DFT calculations (PBEh-3c/def2-mSVP­(C,H,N,O)/def2-mTZVP­(Mn)) (Figures S11–S14) and compared with the experimentally obtained frequencies (Table and Figures S12–S14). In addition, we compared the assigned vibrational modes with previous reports. ,,,, …”

“…(Abbreviations: bend., bending; str., stretching; ip, in-plane). b IR data from previously reported comparable compounds are included for comparison. c of the solid state. d One T 1 u and E g modes are mixed together at 2184 cm –1 leading to two IR observable modes. e L tri = 5,5′-(2-isocyano-5-methyl-1,3-phenylene)­bis­(2-(3,5-di- tert -butyl-2-isocyanophenyl)­thiophene). f L bi = 2,5-bis­(3,5-di- tert -butyl-2-isocyanophenyl)­thiophene. g The peak shows a shoulder at lower wavenumbers h Approximated local symmetry O h i Due to a breakdown of the T 1 u degeneracy …”