Synthesis and crystal structure of an expanded square grid metal organic material, [Cu(L1)(DMF)] _n· (2.64 DMF)

A new square grid metal organic material, [Cu(L1)(DMF)] _n· (2.64 DMF) (1; L1= N-(4-carboxyphenyl)-trimellitimide), has been prepared by solvothermal reaction of Cu(NO ₃) ₂·2.5H ₂O, H ₂L1, and caffeine in N,Ndimethylformamide (DMF). The title compound crystallizes in the monoclinic crystal system, space group C2/c, with a = 18.5176 (6) Å, b = 23.7473 (7) Å, c = 18.1998 (5) Å, b = 107.527 (2)°, and V = 7631.7 (4) Å ³. The undulating sheets, formed by linking of Cu ₂(μ ² -CO ₂) ₄ square paddlewheel nodes by the angular L1, stack to form large square channels of approximately 11.9 9×11.9 Å ² running along the c axis. The geometry and conformation of the linker result in slight distortion of the grids. Further, the 147° bend angle between coordinating moieties of L1 is amenable to forming a diverse array of paddlewheel-based supramolecular isomers.