Telltale Diamagnetism at 50 K of a Coordination Polymer System

The synthesis of coordination polymers (e.g., Prussian blue) is as old as modern chemistry itself, but never stops surprising people. We here report superconductivity observed of a designer coordination polymer system sporting the chemically soft mercaptan and hard carboxyl groups. The mercapto-carboxyl (dubbed Mercarb, or QiuSuo in Mandarin Pinyin) synergy hints at Daoism and here carries over from the molecular to the solid state: the soft sulfur donors bond with Co2+/Ni2+ (or other transition metal ions) to afford 2D sheets for charge transport, while the interlayer metal-carboxylate domain is more ionic and mediates the transition into the superconductive state. Besides the flexible QiuSuo design, this CP system is suited for doping (e.g., with μ2-OH2 units to effect charge balance by transforming into μ2-OH-), in order to fine-tune the electron-hole balance, and to achieve high-temperature superconductivity.