Synthesis of new structurally constrained tetraaza macropolycyclic compounds containing two rigid bridges: Crystal structure and chemical properties of a copper(II) complex

New topologically constrained tetraaza macropolycycles L-9, L-10, and L-11 containing two o-xylylene (-(CH2)C6H4(CH2)-) bridges have been prepared by the reaction of 1,2-bis(bromomethyl) benzene with 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0(7.12)]docosane (L-1), 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L-2), or 2,5,5,7,9,12,12,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L-3). The macropolycycle L-9 readily reacts with Cu2+ ion to form [CuL9](2+) in wet methanol. However, L-10 and L-11 do not bind the metal ion in similar conditions. The Cu-N distances [2.048(4)-2.070(4)] and the ligand field strength of [CuL9](ClO4)(2) are considerably longer and weaker, respectively, than those of other related macropolycyclic copper(II) complexes containing two N-(CH2)(2)-N or N-(CH2)(3)-N bridges. The copper(II) complex is extremely stable even in low pH and quite inert against ligand substitution with CN ion. (C) 2013 Elsevier B.V. All rights reserved.This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2010-0007251)