New discrete and polymeric supramolecular architectures derived from dinuclear (bis-β-diketonato)copper(ii) metallocycles

Abstract

New examples of adducts between di-(and, in one instance, tetra-) functional nitrogen ligands and planar 'platform-like' dinuclear copper(II) complexes, [Cu 2 L 2 ], incorporating the 1,3-aryl linked bis-b-diketonato bridging ligand 1,1 -(1,3-phenylene)-bis(4,4-dimethylpentane-1,3-dione) (H 2 L) have been synthesised. The X-ray structures of six adduct species are reported. The interaction of [Cu 2 (L) 2 ] with the ditopic ligand aminopyrazine (apyz) yielded the sandwich-like tetranuclear species [(Cu 2 L 2 (apyz)) 2 ]. A variable-temperature magnetochemical investigation of this product indicated weak antiferromagnetic coupling between the (five-coordinate) copper centres, mediated by the 2-aminopyrazine linkers. An analogous structure, [(Cu 2 L 2 (dabco)) 2 ] (dabco = 1,4-diazabicyclo[2.2.2]octane), was generated when dabco was substituted for aminopyrazine while use of 4,4 -dipyridyl sulfide (dps) and 4,4 -(1,3-xylylene)-bis(3,5-dimethylpyrazole) (xbp) as the ditopic 'spacer' ligands resulted in polymeric species of type [Cu 2 L 2 (dps)] n and [Cu 2 L 2 (xbp)] n , respectively. These latter species exist as one-dimensional chain structures in which copper(II) centres on different dinuclear platforms are linked in a 'zigzag' fashion. In contrast, with 2,2 -dipyridylamine (dpa) a discrete complex of type [Cu 2 L 2 (dpa) 2 ] formed in which one potential pyridyl donor from each 2,2 -dipyridylamine ligand remains uncoordinated. The use of the potentially quadruply-bridging hexamethylenetetramine (hmt) ligand as the linker unit was found to give rise to an unusual two-dimensional polymeric motif of type [(Cu 2 (L 2 ) 2 ) 3 (hmt) 2 ] n . The product takes the form of a (6,3) network, incorporating triply bridging hexamethylenetetramine units.

Hierarchical assembly of discrete copper(ii) metallo-structures from pre-assembled dinuclear (bis-β-diketonato)metallocycles and flexible difunctional co-ligands

“…2) has five-coordinate copper(II) centres with two planar dinuclear metallocyclic units bridged by two dmpip ligands such that the overall structure is a discrete tetranuclear architecture similar to those previously reported by us using dabco and pyrazine as bridging ligands. 13,20 However, in contrast to these previous structures, the present structure is somewhat 'stepped' resulting from the presence of the chair conformation of the respective bound dmpip ligands. This results in the mean planes of the two dinuclear platforms being separated by 6.35 Å -considerably less than occurs in the tetranuclear analogues incorporating 'linear' dabco (7.73 Å) or pyrazine (7.5 Å) as the bridging co-ligands.…”

Hexamethylenetetramine: An old new building block for design of coordination polymers

“…Three different procedures were reported for the synthesis of [Mn 2 ( 3 -mal) 2 ( 2 -hmt)(H 2 O) 2 ] n (53), which can be obtained by self-assembly from manganese(II) chloride in alkaline aqueous [35a] Apart from the simple self-assembly methods (see above) for the synthesis of coordination polymers of hmt, other reported routes (some of them can also be considered as self-assembly) include the following types: a controlled hydrothermal synthesis (for 8, 10-12 [17]. Examples of the layering synthetic procedure concern 2D [Cu 3 ( 2 -pbpd) 3 ( 3 -hmt)] n (35) [24] and 3D [Cu 3 ( 2 -pbhd) 3 ( 3 -hmt)] n (62) [26a] polymers that were crystallized upon layering the THF solutions of hmt and [Cu 2 ( 2 -pbpd) 2 ] or [Cu 3 ( 2 -pbhd) 3 ], respectively. Slow diffusion techniques were applied for the synthesis of the most intricate metal-hmt networks in [Cu 2 ( 2 -prop) 4 ( 4 -hmt)( 3 -hmt) 2 ] n (34) [41] and 17 (H 2 O) 102 ] n (Cl) 68n ·46nH 2 O·68nDMF (57) [29].…”

“…Yet another approach consists in using the predefined multimetal building blocks (cluster nodes) in combination with hmt as a linker. For example, such a method was successfully applied to the assembly of 2D (in 35) and 3D (in 62 and 63) networks [24,26] via the hmt-linkage of the [Cu 2 ( 2 -pbpd) 2 ], [Cu 3 ( 2 -pbhd) 3 ] or [Cu 3 ( 2 -bpbpd) 3 ] units.…”

“…Taking into consideration only the metal-hmt interactions, two types of topologies were identified (Scheme 3), namely the honeycomb-like hexagons in [Cd 3 Br 6 ( 3 -hmt) 2 (H 2 O) 5 ] n ·n(hmt)·6nH 2 O (38) [12], [Cd 3 (ac) 6 ( 3 -hmt) 2 (H 2 O) 3 ] n ·6nH 2 O (40) [10] and [Cu 3 ( 2 -pbpd) 3 ( 3 -hmt)] n (35) [24], and the periodically tiled pentagons in [Cu 2 ( 2 -prop) 4 ( 4 -hmt)( 3 -hmt) 2 ] n (34) [41].…”

“…The copper(II) polymer 35 [24] is built from the fused chiral hexagons [(Cu 2 ) 6 (hmt) 6 (pbpd) 12 ] that possess a very distorted topology. The infinite 2D layers of 38, 40 and 35 are undulating and thus exhibit the bent honeycomb-like topologies.…”