Synthesis and complexation studies of 16-membered [1+1] selenaaza- and some related macrocycles

A novel 16-membered 1+1] unsymmetrical selenaaza Schiff base macrocycle, 8,9,10,11-tetrahydo-7H-dibenzo-d,o]1,3,7,10,13]diselenatriazacyclohexadecine (5) with N₃Se₂ donor set, has been synthesized by cyclocondensation of di(o-formylphenylseleno)methane and diethylenetriamine. Reduction of 5 with NaBH₄ afforded 6,7,8,9,10,11,12,13-octahydro-5H-dibenzo-d,o]1,3,7,10,13]diselenatriazacyclohexadecine (6). Macrocycle, 10,11,12,13,14,15,16,26,27,28,29,30,31,32-tetradecahydrotetrabenzob,k,n,w]1,13,5,9,17,21]diselenatetraazacyclotetracosine (2b) was synthesized similarly from di(o-formylphenyl)selenide and 1,3-diaminopropane followed by reduction with NaBH₄. Single crystal X-ray structures of 5 and 2b have been determined. Attempted complexation reactions of 5 with Zn(II), Cd(II), Hg(II), Pd(II) and Cu(II) ions and those of 6 with Ag(I), Hg(II) and Pd(II) ions are reported. 28-Membered selenaaza macrocycle 2c on reaction with HgCl₂ and NH₄PF₆, provided a dinuclear Hg(II) complex 9. Complex 9 has been characterized by single crystal X-ray structure.