Heterometallic Mixed‐Valence Copper(I,II) Cyanides that were Tuned by Using the Chelate Effect: Discovery of Famous Cairo Pentagonal Tiling and Unprecedented (3,4)‐Connected {8³}₂{8⁶} Topological 3D Net

Abstract

By using environmentally friendly [Ni(CN)4](2-) as a cyanide source, three new heterometallic cyano-bridged mixed-valence Cu(I)/Cu(II) coordination polymers with three different electronic configurations (d(8)-d(10)), that is, [Cu2Ni(CN)5(H2O)3] (1), [Cu2Ni(CN)5(pn)H2O] (2), and [Cu3Ni(CN)6(pn)2] (3, pn = 1,2-propane diamine) have been synthesized by gradually increasing the amount of pn. Compound 1, which was hydrothermally synthesized in the absence of pn ligand, exhibits the famous 2D Cairo pentagonal tiling, in which the Cu(I), Cu(II), and Ni(II) atoms act as trigonal, T-shaped, and square-planar nodes, respectively. Notably, there are three water molecules located at the meridianal positions of the octahedrally coordinated Cu(II) atom in compound 1. A similar reaction, except for the addition of a small amount of pn, generated a similar Cairo pentagonal tiling layer in which two of the water molecules that were located at the meridianal positions of the octahedrally coordinated Cu(II) atom were replaced by a chelating pn group. Another similar hydrothermal reaction, with the addition of a larger amount of pn, yielded compound 3, which showed a related two-fold-interpenetrated (3,4)-connected 3D framework with an unprecedented {8(3)}2{8(6)} topology in which the Cu(II) atom was chelated by two pn groups. These structural changes between compounds 1-3 can be explained by the chelating effect of the pn group. The replacement of two meridianally coordinated water molecules on the octahedral Cu(II) atom in compound 1 by a pn group gives compound 2, which shows similar Cairo tiling, and a further increase in the amount of pn results in the formation of the [Cu(NC)2(pn)2] unit and the two-fold-interpenetrated 3D framework of compound 3. The mixed-valence properties of compounds 1, 2, and 3 were confirmed by variable-temperature magnetic-susceptibility measurements.

Coordination Polymers and Cage-Containing Frameworks in Uranyl Ion Complexes with rac- and (1R,2R)-trans-1,2-Cyclohexanedicarboxylates: Consequences of Chirality

“…However, the metrics of the (nonplanar) pentagons here is of course different from that in the classical Cairo tiling and the network is visually closer to the topologically equivalent basketweave tiling since, while the four edges ending in a Cd II vertex have close to the same length, that containing the uranyl cation linker is nearly twice as large. Few examples of the Cairo tiling topological type have been reported in metal–organic assemblies, , and, to the best of our knowledge, none in a uranyl compound. As in complexes 1 – 4 and 8 , the cyclohexyl rings protrude on both sides of the layers, and the packing does not contain free spaces (KPI 0.72, or 0.69 with solvent excluded).…”

Control of Structures and Emission Properties of (CuI)n 2-Methyldithiane Coordination Polymers

“…The design of coordination polymers with a predictable secondary building unit (SBU) and dimensionality is a quasi-impossible task but the quest remains of great interest for the discovery of new materials with desired properties such as gas adsorption, [1][2][3][4][5][6][7][8][9] sensing, [10][11][12][13][14][15] thermochromism, [16][17][18][19] magnetism, [20][21][22][23][24] conductivity, [25][26][27][28] redox-activity, 29,30 catalysis, 13,[31][32][33] nonlinear optical behavior 34,35 and luminescence. 8,[36][37][38][39][40] Recent reviews on CPs formed by mono-and dithioethers with CuX salts (X = Cl, Br, I) [41][42][43][44][45][46]…”

“…The design of coordination polymers with a predictable secondary building unit (SBU) and dimensionality is a quasi-impossible task, but the quest remains of great interest for the discovery of new materials with desired properties such as gas adsorption, − sensing, − thermo-chromism, − magnetism, − conductivity, − redox-activity, , catalysis, ,− nonlinear optical behavior, , and luminescence. ,− Recent reviews on CPs formed by mono- and dithioethers with CuX salts (X = Cl, Br, I) − revealed that, when X = I, the SBU had a strong tendency to form closed cubanes (Cu 4 I 4 ) and 1D staircase polymeric structures, whereas the rhomboid Cu 2 X 2 S 4 SBU is predominately noted when X = Cl or Br. The key property is that the cubanes show luminescence regardless of the ligand, whereas the rhomboids and staircase motifs are almost always weakly or not emissive. ,, Also, the presence of 2D and 3D CPs increases drastically when semirigid or rigid dithioethers are used as assembling ligands. ,, The interest in 2D and 3D CPs stems from the possibility to form MOF-like materials .…”

Two-Dimensional Metal-Organic Framework Materials: Synthesis, Structures, Properties and Applications

“…Interestingly, all of the 4-coordinated Ln­(III) centers are in a row and all of the Cu­(I) centers occupy alternate rows in the pentagon tiling. Such Cairo tiling structures (Figure b) has also been observed in other 2D MOFs. − …”