DESIGN AND CONSTRUCTION OF A NEW CLASS OF SCAFFOLDING-LIKE MATERIALS COMPRISING INFINITE POLYMERIC FRAMEWORKS OF 3-D-LINKED MOLECULAR RODS - A REAPPRAISAL OF THE ZN(CN)2 AND CD(CN)2 STRUCTURES AND THE SYNTHESIS AND STRUCTURE OF THE DIAMOND-RELATED FRAMEWORKS [N(CH3)4][CUIZNII(CN)4] AND CUI[4,4',4'',4'''-TETRACYANOTETRAPHENYLMETHANE]BF4.XC6H5NO2

It is proposed that a new and potentially extensive class of scaffolding-like materials may be afforded by linking together centers with either a tetrahedral or an octahedral array of valences by rodlike connecting units. Some simple general principles concerning the design and construction of these frameworks are presented together with reasons for expecting them to show unusual and useful properties. Two of the simplest conceivable systems of this type are isomorphous Zn(CN)2 and Cd(CN)2 whose structures have been reexamined by single-crystal X-ray diffraction, confirming the earlier description based on powder diffraction data of two interpenetrating diamond-related frameworks: cubic with space group P43m, Z = 2; a = 5.9002 (9) Å (Zn(CN)2) and 6.301 (1) Å (Cd(CN)2); two unique metal centers, one surrounded tetrahedrally by 4 C and the other by 4 N donors; MCNM rods linear; ZnC, 1.923 (6) Å; ZnN, 2.037 (5) Å; CdC, 2.099 (5) Å; CdN, 2.196 (4) Å; CN, 1.150 (5) Å in Zn(CN)2 and 1.162 (5) Å in Cd(CN)2. The interpenetration of separate frameworks demonstrated in these archetypal structures is likely to be a major concern in future studies of more complex scaffolding materials. The material [N(CH3)4][CuZn(CN)4] was deliberately designed to demonstrate one conceivable way of preventing interpenetration; its structure was determined by single-crystal X-ray diffraction: cubic, F42m, a = 11.609 (3) Å, Z = 4. The structure contains a single diamond-related framework with alternating tetrahedral Cu(I) and Zn(II) centers and linear rods that are very likely of the type CuCNZn with bond distances CuC, 1.877 (8) Å; and ZnN, 2.069 (15) Å. N(CH3)4+ ions occupy half the adamantane cavities generated by the framework, the remaining cavities being vacant. CuI[4,4',4'',4'''-tetracyanotetraphenylmethane]BF4·xC6H5NO2(x ≥ 7.7) represents the first attempt to generate an infinite 3D framework with rods of some complexity. The structure was determined by single-crystal X-ray diffraction; tetragonal, I4m2, a = 13.620 (2) Å, c = 22.642 (2) Å, Z = 2. The structure contains a diamond-related cationic framework with C-C6H4-CN-Cu rods of length 8.856 (2) Å. The framework is tetragonally elongated along the c axis apparently as a result of nonbonded interactions between the eight ortho-hydrogen atoms around the methane carbon centers. There is no interpenetration. The framework generates very large admanantane-like cavities occupied by disordered C6H5NO2 (at least 7.7 molecules per Cu) together with BF4- ions. The crystals undergo ready anion exchange. The material is unusual in that approximately two-thirds by volume of what is undoubtedly a crystal is effectively liquid. The results provide confidence that a wide range of scaffolding-like solids should prove accessible. © 1993, IEEE. All rights reserved. © 1990, American Chemical Society. All rights reserved.