Structure and Magnetic Studies on a Series of Two-Dimensional Iron(II) Framework Materials with Varying Ligand Characteristics

Abstract

Targeting the general (4,4)-grid structural motif, we have prepared seven new coordination polymers in the general family [Fe(NCX)2(L)2]·(guest) (L = bis-pyridyl-type bridging ligands; X = S, Se) as an extension of the well-established spin crossover framework (SCOF) family. In all cases, the (4,4)-grid topology is formed by the bridging of octahedral iron(ii) sites in the equatorial plane by bis-pyridyl ligands of varying length, flexibility, and intermolecular interaction capacity. In particular, the six ligands n-(4-pyridyl)-isonicotinamide (pin), trans-1,2-bis(4′-pyridyl)ethane (tvp), 1,2-dibromo-1,2-bis(4′-pyridyl)ethane (dbbpe), bis(4-pyridyl)-1,2,4,5-tetrazine (bptz), 4,4′-bis(pyridyl)acetylene (bpac), and 1,4-bis(4-pyridylethynyl)benzene (bpeben) have been utilised. The seven new materials [Fe(NCS)2(pin)2]·2(MeCN) (pin-S), [Fe(tvp)2(NCS)2]·1/2(tvp)·(CH3CH2OH) (tvp-S), [Fe(dbbpe)2(NCS)2]·6(CH3CN) (dbbpe-S), [Fe(NCS)2(bptz)2]·2(CHCl3)·6(EtOH) (bptz-S), [Fe(NCSe)2(bptz)2]·4(CHCl3)·(EtOH)·(H2O) (bptz-Se), [Fe(NCS)2(bpac)2]·2(PrOH) (bpac-S), and [Fe(NCS)2(bpeben)2]·2(CHCl3) (bpeben-S) all form (4,4)-grids of varying size that are arranged in a parallel stacked topology. Despite being in the [FeN6] coordination environment known to be conducive to spin crossover, these materials all remain high-spin with thermal variation. These results are discussed in context with the large family of SCOFs that show varied spin crossover behaviours.

Influence of Host–Guest and Host–Host Interactions on the Spin-Crossover 3D Hofmann-type Clathrates {FeII(pina)[MI(CN)2]2}·xMeOH (MI = Ag, Au)

“…The spin crossover properties of these compounds turned out to be highly dependent on the solvent content which in turn was intimately interacting with the pina ligand via H-bonding. Similarly, the not-SCO-active 2D compound [Fe II (NCS) 2 ( pina ) 2 ]·2­(CH 3 CN) not only presents H-bonds between the amide moieties and the acetonitrile molecules but also between the pina ligands through CO···HN contacts . Here, we have implemented, for the first time, the bridging pina ligand to build a 3D structure that exhibits accessible void volume, ca.…”

“…Similarly, the not-SCO-active 2D compound [Fe II (NCS) 2 (pina) 2 ]•2(CH 3 CN) not only presents H-bonds between the amide moieties and the acetonitrile molecules but also between the pina ligands through CO•••HN contacts. 30 Here, we have implemented, for the first time, the bridging pina ligand to build a 3D structure that exhibits accessible void volume, ca. 40%, where methanol molecules can be trapped affording an infinite lattice of H-bonds.…”

“…Here, we report on the synthesis, crystal structures, and magnetic behavior of two new doubly interpenetrated 3D Hofmann-type clathrates formulated as {Fe II ( pina )­[M I (CN) 2 ] 2 }· x MeOH [being x a value between 0 and 5; pina = N -(pyridin-4-yl)­isonicotinamide (Figure a); M I = Ag I and x ≈ 5 ( 1· x MeOH ) or M I = Au I and x ≈ 5 ( 2· x MeOH )] and its desolvated forms 1 and 2 ( x = 0). The novelty of the pina bridging ligand, which was previously used to design other SCO-active (and -inactive) Fe II complexes, is that both carbonyl and −NH moieties of the amide group are susceptible of interacting via H-bonding with the adsorbed guest molecules. Indeed, our magnetic characterizations show a strong impact of the presence of intrapore methanol guest molecules on the SCO properties and, in particular, reveal the generation of hysteretic multistep spin transitions presumably related to the presence of host–guest H-bonding interactions.…”

1,2,4,5-Tetrazine based ligands and complexes

“…The same authors have reported a poly-knotted 3D structure after coordination of 4,4'-bptz with Cd(II) metal ions. 81 4,4'-bptz has been coordinated to more divalent metal ions, such as Mn(II), 82 Fe(II) 83 and Ni(II), 73 to afford neutral CPs. In the 3D CP [Mn(4,4'-bptz)(N3)2], 84 In the ten last years, the adsorption properties of 4,4'-bptz-based MOFs have been thoroughly investigated.…”

Celebrating Professor Len Lindoy’s 80th Birthday

“…[15] Stuart Batten, Keith Murray, David Turner, and Glen Deacon at Monash University present transition metal thiocyanate complexes of picolylcyanoacetamides, [16] and Suzanne Neville from Sydney brings us an investigation into the structure and magnetic properties of a series of two-dimensional iron(II) framework materials. [17] Peter Junk, currently Nevitt Professor of Chemistry at JCU where Len was based for the bulk of his career, reports on the synthesis and structures of rare earth 3-(4 0 -methylbenzoyl)-propanoate complexes and their properties as new corrosion inhibitors. [18] Deanna D'Alessandro (Sydney), who undertook her Ph.D. at JCU with Richard Keene, presents findings of the in situ spectroelectrochemical investigation of ruthenium(II) complexes with bispyrazolyl methane triarylamine ligands.…”