Two-Dimensional Anisotropic Flexibility of Mechanically Responsive Crystalline Cadmium(II) Coordination Polymers

Crystals of a family of six one-dimensional (1D) coordination polymers of cadmium(II) with cyanopyridines [[CdX2L2]n, where X = Cl, Br, or I and L = 3-cyanopyridine (3CNpy) or 4-cyanopyridine (4-CNpy)] presented a variety of morphologies and mechanical responses with dominant twodimensional (2D) anisotropic flexibility, which has not been previously reported. All mechanically adaptable crystals were 2D flexible and displayed a variety of direction-dependent responses; in addition to 2D isotropic flexibility observed for solely elastic materials, 2D anisotropic flexibility was noticed for both elastic and elastic -> plastic crystals. The consequences of fine and controlled structural variations on mechanical behavior were additionally explored via microfocus single-crystal X-ray diHraction and complementary theoretical studies, revealing that the relative strength and direction of the hydrogen bonding interactions were the key parameters in delivering a specific mechanical response.

Automated summary

This article presents the crystal structure and mechanical properties of a family of one-dimensional coordination polymers, which exhibit two-dimensional anisotropic flexibility. The study reveals that the relative strength and direction of hydrogen bonding interactions play a crucial role in determining the mechanical response.