Supramolecular Chains and Coordination Nanowires Constructed of High-Spin Co^II₉W^V₆ Clusters and 4,4′-bpdo Linkers

Abstract

Cyanido-bridged high-spin {Co II [Co II -(MeOH) 3 ] 8 [W V (CN) 8 ] 6 } (Co 9 W 6 ) clusters revealing singlemolecule magnet behavior were combined with 4,4′bipyridine-N,N′-dioxide (4,4′-bpdo) linkers, giving unique Hbonded supramolecular {Co II 9 (MeOH) 24 [W V (CN) 8 ] 6 }•4,4′bpdo•MeOH•2H 2 O (1) chains and one-dimensional coordin a t i o n { C o I I [ C o I I ( 4 , 4 ′ -b p d o ) 1 . 5 ( M e O H ) ] 8 [ W V -(CN) 8 ] 6 }•2H 2 O (2) nanowires. The hydrogen-bonded chains of 1 are embedded within the three-dimensional supramolecular network stabilized by the series of noncovalent interactions between Co 9 W 6 clusters, 4,4′-bpdo, and solvent molecules. The coordination nanowires 2, revealing an average core diameter of about 11 Å, are arranged parallel with the significant separation in the crystal structure, leading to a microporous supramolecular network with broad channels (12 × 12 Å) filled by methanol and water. Both 1 and 2 are stable only in a mother solution or an organic protectant, whereas they undergo the fast exchange of methanol ligands to water molecules during drying in the air. Synthesized materials preserve the magnetic characteristics of Co 9 W 6 clusters with an effective ferromagnetic coupling, giving a ground-state spin of 15/2. For 2, the additional antiferromagnetic intercluster interactions are observed. Below 3 K, the frequency-dependent χ M ″(T) signals of 1 and 2 indicate the onset of slow magnetic relaxation. For 1, the relaxation time follows the Arrhenius law with an energy gap of Δ/k B = 10.3(5) K and τ 0 = 4(1) × 10 −9 s, which is consistent with single-molecule magnet behavior.

Tuning of High Spin Ground State and Slow Magnetic Relaxation within Trimetallic Cyanide‐Bridged {NiIIxCoII9−x[WV(CN)8]6} and {MnIIxCoII9−x[WV(CN)8]6} Clusters

“…The DC χT ( T ) and M ( H ) data for the Mn x Co 9− x W 6 series are presented in Figure and Table S7. The χT values at 300 K lie close to the ranges calculated for uncoupled spins, assuming g W =2.0, S W = 1 / 2 , g Mn =2.0, S Mn = 5 / 2 , g Co =2.7–3.4, and S Co = 3 / 2 (Figure a) ,,,. Contrary to the former case of the NiCoW series, significant changes occur along the whole range of x .…”

Optical Activity and Dehydration-Driven Switching of Magnetic Properties in Enantiopure Cyanido-Bridged CoII3WV2 Trigonal Bipyramids

“…65,66 The magnetization of 1 measured as a function of the external magnetic field at 2 K does not saturate to 50 kOe, reaching a value of 8.0 μ B , but tends roughly in an asymptotic manner limit of 8.5 μ B , which is expected for ferromagnetic alignment of Co II and W V magnetic moments within the {Co II 3 W V 2 } units ( Figure 6b). 5,33,67 There is no detectable signal in the out-of-phase magnetic susceptibility above 1.8 K precluding the SMM behavior of 1.…”

Structural Disorder in High-Spin {CoII9WV6} (Core)-[Pyridine N-Oxides] (Shell) Architectures

“…The ligand shell disorder in 1 and 2 is unprecedented along the entire family, and may be understood in terms of the degree of M-L bond rigidity and intercluster interactions inscribed in the ligand structure and M-L bonding mode. The longer linker ligands (e.g., 4,4 -bipyridine mono-N-oxide, 4,4 -bpmo; 4,4 -bipyridine di-N-oxide, 4,4 -bpdo) [16,17] form quite easily the bridging connections between clusters, and/or participate in the hydrogen bond supramolecular interaction network. On the other hand, the convergent bidentate ligand (frequently equipped with the remote substituents, e.g., 4,4 -dimetyl-2,2 -bipyridine, 4,4 -di-tert-butyl-2,2 -bipyridine, or 4,7-di-phenyl-1,10-phenantroline) [20] fill the intercluster space with the π-π synthons or van der Waals contacts.…”

“…Along this line, investigation of the crystalline phases composed of six capped body-centered cube Co 9 M' 6 clusters as molecular platforms for magnetic relaxations suggests the following image of structure-properties correlations. Twelve compounds were studied structurally and magnetically, counting the original {Co 9 M 6 (MeOH) 24 }•solv (M = Mo, W) phases [12] and those equipped with various ligands: chelating, 2,2 -bipyridine-N-oxide (2,2 -bpmo) [13], 2,2 -bipyridine-N,N'-dioxide (2,2 -bpdo) [14], and methylpyridinemethanol (mpm) [15], as well as bridging 4,4 -bipyridine-N-oxide (4,4 -bpmo) [16], 4,4 -bipyridine-N,N'-dioxide (4,4 -bpdo) [17], and pyrazine-N-oxide (pzmo) [16]. The unequivocal direct fitting of lnτ(T −1 ) point set using the Arrhenius law was possible only in the case {Co 9 W 6 (2,2 -bpdo) 6 (MeOH) 12 }{Co 9 W 6 (2,2 -bpdo) 7 (MeOH) 10 }•8H 2 O•2MeCN•27MeOH to give the best ∆E/k B of 30.0(8) K along the whole series [14].…”