A series of functional 2-phenyl-3H-[1,2,4]­triazino­[5,6,1-kl]­phenoxazin-3-yl (planar Blatter) radicals containing CO2Me, CN, and NO2 groups at the C(10) position and 2-phenyl-3H-pyrido­[3,2-b]­[1,2,4]­triazino­[1,4]­benzoxazin-3-yl have been obtained in yields of 40–80% by using the Pschorr-type cyclization and characterized by spectroscopic (ultraviolet–visible and electron paramagnetic resonance), electrochemical, and density functional theory methods. Two of these groups, CO2Me and NO2, have been transformed into CO2H and NH2, respectively, and conjugated with amino acids. One of the derivatives was analyzed by single-crystal X-ray diffraction methods.

A series of 19 structurally diverse C(3)substituted derivatives of benzo [e][1,2,4]triazine were synthesized from 3-chloro-(1c) and 3-iodobenzo[e][1,2,4]triazine (1d) obtained in three steps from 2-nitroaniline in 37−55% yields. Nucleophilic aromatic substitution and metal-catalyzed (Pd, Cu) reactions led to functional derivatives that include alkyl (C 5 H 11 ), (het)aryl (Ph, 2-thienyl, ferrocenyl), ArCC, amine (NHPh and morpholine), PO(OEt) 2 , sulfanyl (SBu-t), alkoxide (OEt, OMe), and CN. The synthesis of C(3)−CF 3 derivative 1g via the Ruppert reaction with 1d and its 1-oxide analogue 2d led to the substitution followed by formal addition of HCF 3 to the CN bond. Pd-catalyzed carbonylation reactions of 1d and 2d did not give the corresponding C(3)-carboxylic acids. Therefore, acid 1f was obtained through hydrolysis of the CN. The substituent effect on the electronic structure of the benzo[e][1,2,4]triazine ring was investigated by spectroscopic methods (UV−vis and NMR) augmented with density functional theory calculations. Results show significant effect of the C(3) substituent on the π−π*(1) transition energy and good correlation of the 1 H NMR chemical shift with the substituent constant σ p . Molecular and crystal structures of six derivatives were established with the single-crystal X-ray diffraction method, and the substituent impact on the molecular geometry was investigated.

A series of 3-substituted 1-phenyl-1,4-dihydrobenzo­[e]­[1,2,4]­triazin-4-yls 1 was prepared by addition of PhLi to 3-substituted benzo­[e]­[1,2,4]­triazines 2 followed by aerial oxidation. The scope of the C(3) substituents in the reaction was investigated, and 10 structurally diverse radicals 1 were isolated, their stability was assessed and properties were investigated with spectroscopic and electrochemical methods. Two radicals were analyzed with single-crystal XRD methods. Experimental data are compared to DFT results and correlated with Hammett substituent parameters.

The electronic structure of Blatter radical and a series of C(10)-substituted derivatives of 2-phenyl-3H-[1,2,4]triazino[5,6,1-kl]phenoxazin-3-yl (planar Blatter radicals) containing H, F, Cl, Br, CN, CF3 and OMe substituents was investigated by...