Identification of new chromium(III) nitrito complexes by means of the electronic spectrum of the nitro ligand in dipolar aprotic solvents

Chromium(III) Complexes for Photochemical Nitric Oxide Generation from Coordinated Nitrite: Synthesis and Photochemistry of Macrocyclic Complexes with Pendant Chromophores, trans-[Cr(L)(ONO)2]BF4

“…Under the roughly D 4 h symmetry of these complexes, this band would split into 4 B 2g and 2 E 2g components, but such splitting is not obvious here. The position of this band is in good agreement with those found for previously characterized chromium(III) nitrito complexes. , The peak centered at 328 nm (ε = 271 M -1 cm -1 ) for II and at 334 nm (243 M -1 cm -1 ) for IV has been assigned as an intraligand n−π* transition localized to the coordinated nitrite in analogy to assignments by Fee and Harrowfield 13 for the complex trans -[Cr(en) 2 (ONO) 2 ]ClO 4 . This band tails out to ∼400 nm and apparently obscures the higher energy quartet absorptions expected for a D 4 h Cr(III) diacido tetraamine complex (found at ∼370 nm for the dichloro analogues) .…”

“…The FTIR absorbance spectra recorded for II − V in KBr pellets each displayed three bands characteristic of an O-bound nitrito ligand . For example, trans -[Cr(mbc)(ONO) 2 ]BF 4 ( II ) showed bands at 1496 cm -1 (ν as , ONO), 982 cm -1 (ν s , ONO), and 818 cm -1 (δ wag , ONO) in agreement with previously reported chromium(III) nitrito complexes (Supporting Information, Table S1). , Each complex also displayed two relatively weak bands representing the N−H wagging modes of trans-configured cyclam ring, for example, at 878 and 892 cm -1 for II , while the cis isomers would have four bands in this region …”

Magnetic, thermal and spectral behaviour of 3-chloro-2-nitrobenzoates of Co(II), Ni(II), and Cu(II)

“…The IR spectra recorded for the hydrated and dehydrated 3-chloro-2-nitrobenzoates of Co(II), Ni(II) and Cu(II) show that the nitro group is not transformed to the nitrite group with rising temperature. No bands confirming the isomerization of the nitro group through the oxygen atom are observed [22,23].…”

“…As a monodentate ligand, nitrite ion may be bounded either through a nitrogen atom forming the nitro complex or through one of the oxygen atoms yielding a nitrite complex. The general effect of coordination via nitrogen is a rise in the frequencies of both ν as NO 2 and ν s NO 2 compared to the values for free ioñ 1328 cm -1 and ~1260 cm -1 , respectively [23]. The IR spectra recorded for the hydrated and dehydrated 3-chloro-2-nitrobenzoates of Co(II), Ni(II) and Cu(II) show that the nitro group is not transformed to the nitrite group with rising temperature.…”

Understanding Eu3+ Emission by Using 15N Vibronic Shifts

“…We therefore searched for other centrosymmetric systems where a comparison could be made with the spectra of EuF 6 3− and EuCl 6 3− . The versatile nitrite ligand is a suitable candidate because it forms chelating bidentate coordination with lanthanide (Ln 3+ ) ions, unlike the mainly monodentate nitrito and N -ligated nitro complexes with transition metals. − The Ln 3+ ion occupies a T h site in the Cs 2 NaLn(NO 2 ) 6 systems and is surrounded by six NO 2 − ions, as shown in Figure . Some previous investigations , have shown that the electronic spectra are very complex because they are almost entirely vibronic in nature, so that comprehensive investigations have not yet been performed.…”