New Tetrahydro-1,2,4,5-Tetrazinan-3-Ones and Oxoverdazyl Free Radicals

Abstract

A series of tetrahydro-1,2,4,5-tetrazinan-3-ones have been prepared by the reaction of carbonic acid bis (1-methylhydrazide) with aromatic aldehydes. These were oxidised to oxoverdazyl free radicals and used immediately for ESR spectroscopy studies that indicate that the unpaired electron is delocalised over the verdazyl ring. The ESR spectra can be very well simulated considering hyperfine couplings with the four nitrogen atoms of the verdazyl ring and the six hydrogen atoms of the two methyl groups bonded to it.

Conformation and crystal packing sensitivity to substitution of thioxo- and oxo-tetrazane derivatives

“…In a second step, the condensation of 1a or 2a with selected aldehydes leads to the desired products. While 2b-e and 2g have been already reported, 4,7,12,15 only 1b is mentioned in the literature 16 for the thioxo series and, in this case, no further data were presented. The synthesis of six new sulfur-substituted derivatives thus demonstrates the versatility of the synthetic scheme proposed by Neugebauer while the obtained yields demonstrate its efficiency (Scheme 2).…”

“…First, no p stacking is observed in 1c while the combination of p stacking and hydrogen bonding between one NH function of the tetrazane ring and the nitrogen atom of the pyridine of a neighboring molecule in 2c lead to the formation of mixed supramolecular chains which are similar to those encountered in (6-methyl-2-pyridyl)oxotetrazane. 15 Moreover, whereas an intermolecular hydrogen bond involving the CQS group is observed in 1c, there is no such interaction involving the carbonyl function in the corresponding oxo derivative 2c. Such a marked discrepancy is not observed in all the cases.…”

“…The structures of 2b and 2c were previously described 12,15 while no structural data were obtained for 1d, 2d and 2e. We report here the crystal structures of seven compounds (1b-g, 2f-g) whose crystallographic parameters are summarized in Table 1.…”

“…Nevertheless, up to date, this family of molecules has mainly been used as a precursor of verdazyl radicals, promising species in molecular magnetism, [10][11][12][13][14] and little is known about their organisation in the solid state. 9,15 We report herein the synthesis of six original compounds, mainly thione derivatives. We present seven novel crystal structures of tetrazane-based derivatives and compare the conformation of the molecules and the crystal packing of nine of such compounds by analysing the nature of the interactions (hydrogen bonds, p stacking) and the influence of the R substituent and X heteroatom.…”

Versatile synthesis of chiral 6-oxoverdazyl radical ligands – new building blocks for multifunctional molecule-based magnets

“…The displacement of the two C atoms from the ring plane generates a "screw boat" conformation with a puckering parameter (θ = 68.7(7)°) 16 similar to achiral pyridine and pyrazole substituted tetrazinanones. 17,18 Previous studies on tetrazinanone derivatives place the C-substituent either equatorial 17 or axial, 17,18 with equatorial positions favoured for systems capable of undergoing intramolecular hydrogen bonding. In the case of T2b, the pyridine substituent at C1 adopts an equatorial position with respect to the tetrazinanone and is rotated almost perpendicular to the tetrazinanone ring (angle between the two planes: 82.55°), permitting the pyridyl N atom (N1) to form a bifurcated set of intramolecular N⋯H-N hydrogen bonds to N2 and N5 (N1⋯N2 at 2.820(8) Å and N1⋯H-N2 angle of 104(4)°; N1⋯N5 at 2.916(8) Å and N1⋯H-N5 angle of 109(4)°).…”