Conformational isomerism of 1,2-bis(imidazol-1′-yl)ethane in five-coordination polymers: Influence of metal ions and m-isophthalate ligands bearing different substituents

Four novel coordination polymers, {[Zn(gauche-bime)(bdc)] · 0.5H2O}n (1), {[Zn(anti-bime)(HO-bdc)] · 2.5H2O}n (2), [Cu(gauche-bime)0.5(anti-bime)0.5(O2N-bdc)]n (4) and [Ni2(gauche-bime)(anti-bime)(O2N-bdc)2(H2O)2]n (5) were successfully prepared by the solvothermal reactions of 1,2-bis(imidazol-1′-yl)ethane (bime), m-isophthalic acid (H2bdc) or its two derivatives (HO-H2bdc = 5-hydroxyisophthalic acid, O2N-H2bdc = 5-nitroisophthalic acid) with different metal ions. Interestingly, bime in the four complexes exhibit different conformations owing to the synergetic influence of coexistent neutral (–H), electron-donating (–OH) or electron-withdrawing (–NO2) groups of the dicarboxylate ligands and different metal ions. In 1 and 2, only one conformation of bime (gauche in 1 and anti in 2) is displayed, while the mixed conformations of bime (gauche:anti = 1:1) are observed in 4 and 5. At the same time, one previously reported compound {[Zn(anti-bime)(O2N-bdc)] · H2O}n (3) as a comparable substance in the research system was also mentioned, in which the anti-conformation of bime was observed.

The solvothermal reactions of 1,2-bis(imidazol-1′-yl)ethane (bime), m-isophthalic acid (H2bdc) or its derivatives 5-hydroxylisophthalic acid (HO-H2bdc) and 5-nitroisophthalic acid (O2N-H2bdc) with different metal ions gave rise to five novel coordination polymers, {[Zn(gauche-bime)(bdc)] · 0.5H2O}n (1), {[Zn(anti-bime)(HO-bdc)] · 2.5H2O}n (2), {[Zn(anti-bime)(O2N-bdc)] · H2O}n (3), [Cu(gauche-bime)0.5(anti-bime)0.5(O2N-bdc)]n (4) and [Ni2(gauche-bime)(anti-bime)(O2N-bdc)2 (H2O)2]n (5). The presence of coexistent electron-donating and electron-withdrawing groups in dicarboxylate ligands and different metal ions play crucial roles on the conformational preference of bime in the five structures.Figure optionsDownload as PowerPoint slide