The Rule Rather than the Exception: Structural Flexibility of [Ni(cyclam)]²⁺-Based Cyano-Bridged Magnetic Networks

Abstract

Changes in structure and magnetic properties accompanying guest removal, inclusion, or exchange in two CN-bridged 2D networks of honeycomb topology: {[Ni-(cyclam)] 3 [Fe(CN) 6 ] 2 } n (1) and {[Ni(cyclam)] 3 [Cr(CN) 6 ] 2 } n(2) (cyclam = 1,4,8,11-tetraazacyclotetradecane) were studied by PXRD and magnetic measurements. For each compound four pseudopolymorphic forms differing in structure and magnetic characteristics were identified: fully hydrated form stable in water, partly hydrated form stable in the air at ambient conditions, anhydrous form, and MeOH-modified form. All forms can be reversibly transformed into one another by several interconversion pathways, which fully correspond between Fe and Cr compounds. All forms of 1 and 2 are metamagnetic-like with varied T c and critical field H cr . For several forms, differently shaped magnetic hysteresis loops can be observed. For the partly hydrated and MeOH modified forms structure models are proposed on the basis of PXRD data. Correlations between structural features and magnetic properties are discussed.

Solvatomagnetic Studies on Cyano‐Bridged Bimetallic Chains Based on [Mn(cyclam)]3+ and Hexacyanometallates

“…Moreover, some additional peaks that arise after attempted rehydration suggest partial decomposition. This behaviour is dissimilar to the fully reversible changes observed for related 2D and 1D solvatomagnetic structures based on Ni complexes of cyclam. This may be attributed to the formation of a stable hydrogen‐bond network in the dihydrates.…”

“…For several such networks of different dimensionality, the removal or exchange of solvent of crystallisation caused modification of bond lengths and angles and marked deformation of the structure. In most cases the changes were fully reversible and accompanied by modification of magnetic properties . The most pronounced flexibility of the coordination skeleton was found for 2D microporous networks with honeycomb‐like topology.…”

“…The most pronounced flexibility of the coordination skeleton was found for 2D microporous networks with honeycomb‐like topology. Three such assemblies based on octa‐ and hexacyanometallates of the general formula {[Ni(cyclam)] 3 [M(CN) m ] 2 · solv} n (M = Fe or Cr, m = 6;, M =W, m = 8) have been studied. For each of them four interconvertible pseudopolymorphic forms containing different types or amount of guest molecules (solv = H 2 O, MeOH or MeCN) could be obtained.…”

Modification of Structure and Magnetic Properties in Coordination Assemblies Based on [Cu(cyclam)]2+ and [W(CN)8]3−

“…Conversely, there is no connection in the [001] direction, Projections of structure along the crystallographic axes for 1•5H 2 O and 1 (Figure 2) show the ladder-like topology retained upon dehydration. In both structures, the ladders lie in the (11-1) plane and run along the [1][2][3][4][5][6][7][8][9][10] direction. However, the changes in the coordination geometry of the [W(CN) 8 ] 3− ion and different alignment of the cyclam ligand in both forms are noticeable.…”

“…By combining it with different polycyanometallates, we obtained two main families of coordination polymers of 1D and 2D connectivity. The 2D {[Ni II (cyclam)] 3 [M(CN) n ] 2 } ∞ (M = Cr III , Fe III , n = 6; M = W V , n = 8) networks [4][5][6][7] show honeycomb-like topology with microporous channels running across the coordination layers. For these networks, we observed formation of different hydrates as well as the possibility to introduce small organic molecules.…”