Spin-Crossover Behaviors of Iron(III) Compounds with Strong Intermolecular Interactions

Abstract

Iron(III) spin-crossover compounds with H3-OMe-salRen ligands [Fe(3-OMe-salRen)2]ClO4 (1–5) were prepared and characterized by single-crystal X-ray diffraction, Mössbauer spectra, magnetic susceptibilities, and electronic spectra, where 3-OMe-salRen is a tridentate ligand derived from 3-methoxysalicylaldehyde and N-R-ethylenediamine (R = H, Me, Et, Pr, and Bu for 1, 2, 3, 4, and 5). The structures of compounds 1, 2, 3, and 5 at 90 and 298 K, and that of compound 4 at 298 K were determined. Compounds 1, 2, 3, and 5 exhibited a spin transition depending on temperature; the transition temperatures for 1, 2, 3, and 5 were >400, 360, 196, and 223 K, respectively. Compound 4 was in the high-spin state in the temperature range of 5 to 400 K. σ–π or π–π interactions exist in compounds 1–5, and the structures of the compounds were made clear in both the high-spin and low-spin states. Compound 3 exhibited a spin transition with thermal hysteresis.

Unusual Magneto‐Structural Features of the Halo‐Substituted Materials [FeIII(5‐X‐salMeen)2]Y: a Cooperative [HS‐HS]↔[HS‐LS] Spin Transition

“…The room temperature values of χ M T for 1 – 4 , which occur in the range 4.06–4.28 cm 3 K mol −1 , are consistent with the spin‐only value for HS iron(III) (χ M T ≈4.38 cm 3 K mol −1 ). They also concur with literature values in the range 3.80–4.50 cm 3 K mol −1 for closely related ferric spin‐crossover materials; although some of these reported values are somewhat low . The spin conversion in 1 – 4 , evidenced by the decrease in the values of χ M T with temperature, culminates in a plateau with a width of 115 K (140‐25 K) for 2 – 4 and 85 K (110‐25 K) for 1 .…”

“…The tridentate en ‐based salicylaldimine ligands of considerable interest were R′‐HsalRen (R=Et, R′‐HsalEen; Me, R′‐HsalMeen and Bz, R′‐HsalBzen), with the substituent groups R′ (commonly ‐OMe, ‐OEt and ‐NO 2 ) in either the ortho or para positions of the phenolate moiety. Just over a decade ago, this system was extended to the Schiff‐base ligands R′‐HsalPen and R′‐HsalBen (R= n ‐propyl and n‐ butyl, respectively) …”

Synthesis and Crystal Structures of μ‐Oxido‐ and μ‐Hydroxido‐Bridged Dinuclear Iron(III) Complexes with an N2O Donor Ligand – A Theoretical Study on the Influence of Weak Forces on the Fe–O–Fe Bridging Angle

“…The bridging hydroxide O (10) In this context we want to emphasize that most of the previously reported Fe III complexes of tridentate Schiffbase ligands are bis(Schiff base) complexes with noncoordinating counteranions such as ClO 4 -, NO 3 -, and PF 6 -. [16][17][18] Among the mono(Schiff base) complexes, alkoxido bridges (OMe, OEt) are found in three [19][20][21] and double phenoxido bridges in two. [19,22] The presence of a single μ-oxido bridge in 1a, which contains a tridentate N,N,O donor Schiff-base ligand is uncommon, and, to the best of our knowledge, Figure 3.…”

“…[14] We have used tridentate, N 2 O donor Schiff-base ligands extensively to synthesize both discrete and infinite polynuclear complexes of Cu II and Ni II with interesting structures and magnetic properties. [15] Fe III complexes with such ligands are scarce, [16][17][18][19][20][21][22] [23] We have repeated the synthesis and crystal structure determination of 1b in order to confirm the presence of a water molecule interacting with the ligand. This water molecule is crucial in the crystal packing as it influences the Fe-O-Fe angle.…”

Two New Isomeric Di-μ-oxo Bis[oxovanadium(V)] Complexes Containing Schiff Base Ligands

“…In addition, the presence of vanadium haloperoxidases has particularly stimulated the search for the structural and functional models based on vanadium complexes [11,12]. Recently, some dioxovanadium(V) complexes with Schiff base ligands have been reported [13][14][15], and few iron complexes derived from 2-[(2-ethylaminoethylimino)methyl]-6-methoxyphenolate (L 1 ) [16][17][18], and few copper and nickel complexes derived from 2-[(2-ethylaminoethylimino)methyl]-5-methoxyphenolate (L 2 ) [19][20][21] are reported, but the vanadium complexes with tridentate Schiff base ligands derived from N-ethylethane-1,2-diamine have never been reported. Here, we report the synthesis and structures of two new isomeric dioxovanadium(V) complexes, [VO 2 L 1 ] 2 (1) and [VO 2 L 2 ] 2 (2).…”