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One‐Dimensional Ferromagnetically Coupled Bimetallic Chains Constructed with trans ‐[Ru(acac) 2 (CN) 2 ] − : Syntheses, Structures, Magnetic Properties, and Density Functional Theoretical Study
Author(s) -
Guo JunFang,
Wang XiuTeng,
Wang BingWu,
Xu GuanCheng,
Gao Song,
Szeto Lap,
Wong WingTak,
Wong WaiYeung,
Lau TaiChu
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902047
Subject(s) - cyclen , chemistry , crystallography , acetylacetone , antiferromagnetism , bimetallic strip , ruthenium , stereochemistry , inorganic chemistry , catalysis , organic chemistry , physics , condensed matter physics
Four cyano‐bridged 1D bimetallic polymers have been prepared by using the paramagnetic building block trans ‐[Ru(acac) 2 (CN) 2 ] − (Hacac=acetylacetone): {[{Ni(tren)}{Ru(acac) 2 (CN) 2 }][ClO 4 ]⋅CH 3 OH} n ( 1 ) (tren=tris(2‐aminoethyl)amine), {[{Ni(cyclen)}{Ru(acac) 2 (CN) 2 }][ClO 4 ]⋅ CH 3 OH} n ( 2 ) (cyclen=1,4,7,10‐tetraazacyclododecane), {[{Fe(salen)}{Ru(acac) 2 (CN) 2 }]} n ( 3 ) (salen 2− = N , N′ ‐bis(salicylidene)‐ o ‐ethyldiamine dianion) and [{Mn(5,5′‐Me 2 salen)} 2 {Ru(acac) 2 (CN) 2 }][Ru(acac) 2 (CN) 2 ]⋅ 2 CH 3 OH ( 4 ) (5,5′‐Me 2 salen= N,N′ ‐bis(5,5′‐dimethylsalicylidene)‐ o ‐ethylenediimine). Compounds 1 and 2 are 1D, zigzagged NiRu chains that exhibit ferromagnetic coupling between Ni II and Ru III ions through cyano bridges with J =+1.92 cm −1 , z J ′=−1.37 cm −1 , g =2.20 for 1 and J =+0.85 cm −1 , z J ′=−0.16 cm −1 , g =2.24 for 2 . Compound 3 has a 1D linear chain structure that exhibits intrachain ferromagnetic coupling ( J =+0.62 cm −1 , z J ′=−0.09 cm −1 , g =2.08), but antiferromagnetic coupling occurs between FeRu chains, leading to metamagnetic behavior with T N =2.6 K. In compound 4 , two Mn III ions are coordinated to trans ‐[Ru(acac) 2 (CN) 2 ] − to form trinuclear Mn 2 Ru units, which are linked together by π–π stacking and weak Mn⋅⋅⋅O* interactions to form a 1D chain. Compound 4 shows slow magnetic relaxation below 3.0 K with ϕ =0.25, characteristic of superparamagnetic behavior. The Mn III ⋅⋅⋅Ru III coupling constant (through cyano bridges) and the Mn III ⋅⋅⋅Mn III coupling constant (between the trimers) are +0.87 and +0.24 cm −1 , respectively. Compound 4 is a novel single‐chain magnet built from Mn 2 Ru trimers through noncovalent interactions. Density functional theory (DFT) combined with the broken symmetry state method was used to calculate the molecular magnetic orbitals and the magnetic exchange interactions between Ru III and M (M=Ni II , Fe III , and Mn III ) ions. To explain the somewhat unexpected ferromagnetic coupling between low‐spin Ru III and high‐spin Fe III and Mn III ions in compounds 3 and 4 , respectively, it is proposed that apart from the relative symmetries, the relative energies of the magnetic orbitals may also be important in determining the overall magnetic coupling in these bimetallic assemblies.