Magnetostructural Investigation of Orthogonal 1-Aryl-3-Phenyl-1,4-Dihydrobenzo[e][1,2,4]triazin-4-yl Derivatives.

3-Phenyl-1,4-dihydrobenzo[e][1,2,4]triazinyl radicals with the N(1) position substituted with naphth-2-yl (1 b), naphth-1-yl (1 c), pyren-1-yl (1 d), anthracen-9-yl (1 e), 2-trifluoromethylphenyl (1 f), 3-trifluoromethylphenyl (1 g), and 2-iodophenyl (1 h) were characterized by using single-crystal X-ray diffraction, variable-temperature magnetic susceptibility, and DFT computational methods. The substituent at N(1) is essentially orthogonal to the heterocycle plane in 1 f and 1 h, and with a high torsion angle in 1 c and 1 d. Radicals 1 c and 1 h form unusual infinite chains with crisscrossing hetero-co-facial π-π interactions, whereas radical 1 d forms analogous homo-co-facial arrangements. Infinite chains of homo-co-facial π-π dimers are found in 1 b, 1 f and 1 g; in the latter the position of the CF3 group controls the slippage of the dimers in the chain. No π-π parallel arrangements were found in 1 e. Magnetic susceptibility measurements demonstrated strong antiferromagnetic interactions in 1 b (J=-264±4 cm-1 ) and 1 f (J=-134±1 cm-1 ), while weak intradimer ferromagnetic interactions were found in 1 g (J2 =+21±1 and J1 =-15±1 cm-1 ). Other derivatives exhibit typical weak antiferromagnetic exchange interactions in a range of -5 to -10 cm-1 .