Temperature‐induced solid‐to‐solid transformation in helical homochiral coordination polymers

摘要

The reactions of ( R )‐ and ( S )‐4‐(1‐carboxyethoxy)benzoic acid (H 2 CBA) with 1,3‐bis(2‐methyl‐1 H ‐imidazol‐1‐yl)benzene (1,3‐BMIB) ligands afforded a pair of homochiral coordination polymers (CPs), namely, poly[[[μ‐1,3‐bis(2‐methyl‐1 H ‐imidazol‐1‐yl)benzene][μ‐( S )‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] monohydrate], {[Zn(C 10 H 8 O 5 )(C 14 H 14 N 4 )]·H 2 O} n or {[Zn{( S )‐CBA}(1,3‐BMIB)]·H 2 O} n ( 1‐L ), and poly[[[μ‐1,3‐bis(2‐methyl‐1 H ‐imidazol‐1‐yl)benzene][μ‐( R )‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] monohydrate] ( 1‐D ). Three kinds of helical chains exist in compounds 1‐D and 1‐L , which are constructed from Zn II atoms, 1,3‐BMIB ligands and/or CBA 2? ligands. When the as‐synthesized crystals of 1‐L and 1‐D were further heated in the mother liquor or air, poly[[μ‐1,3‐bis(2‐methyl‐1 H ‐imidazol‐1‐yl)benzene][μ‐( S )‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)], [Zn(C 10 H 8 O 5 )(C 14 H 14 N 4 )] n or [Zn{( S )‐CBA}(1,3‐BMIB)] n ( 2‐L ), and poly[[μ‐1,3‐bis(2‐methyl‐1 H ‐imidazol‐1‐yl)benzene][μ‐( R )‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] ( 2‐D ) were obtained, respectively. The single‐crystal structure analysis revealed that 2‐L and 2‐D only contained one type of helical chain formed by Zn II atoms and 1,3‐BMIB and CBA 2? ligands, which indicated that the helical chains were reconstructed though solid‐to‐solid transformation. This result not only means the realization of helical transformation, but also gives a feasible strategy to build homochiral CPs.