Synthesis, Crystal Structures And Magnetic Properties Of Cyanide-Bridged Heterometal Complexes

The study of molecular magnetism is a new rising research field encompassing chemistry, physics, material science and life sciences, which the main task is to study and elucidate the magnetic coupling nature between the spin-carrier in the molecular system, reveal the correlation of structure and magnetism, find and study the complicated magnetism phenomenon, and design and synthesize new molecular-based magnetic materials, such as single-molecular magnet (SMM), single-chain magnet (SCM), high-Tc magnet, spin-crossover material, photomagnetic materials and elec-magnetic bifunctional materials, et al. It should be worth noting that, due to the wide application foreground and the important theoretical significance, the research of molecular magnetism has attracted intense attention of the molecular magnetism chemist over the world. The main purpose of this dissertation is to select and develop suitable cyanide-containing building blocks and all kinds of magnetic spin-carriers, synthesize cyanide-bridged complexes with novel structures by using them under different reaction conditions, and study their structure and magnetic properties with an aim to obtain excellent molecular magnetic materials. The main research contents are as follows:1. Six cyanide-bridged trinuclear sandwich-type MⅢ-MnⅢ-MⅢ(MⅢ= Fe, Cr, Co) complexes and four binuclear cyanide-bridged FeⅢ-MnⅢcomplexes have been synthesized by the reactions of six cyanide-containing building blocks trans-K[M(L)(CN)2](MⅢ= Fe, Cr, Co; L= bpb2-, bpmb2-) and five manganese(Ⅲ)-porphyrin compounds. All the complexes have been characterized by element analysis, IR spectra and X-ray diffraction. Single structure analysis reveal that both the electronic nature and the steric volume of the substituent groups coming from the equatorial plane of the porphyrin have obvious influence on the structure of the formed cyanide-bridged complexes. Investigation over magnetic properties of these heterometallic complexes reveals the ferromagnetic interaction between MnⅢand FeⅢmagnetic centers and antiferromagnetic coupling between MnⅢand CrⅢ. For the ac magnetic susceptibility measurement of cyanide-bridged FeⅢ-MnⅢcomplexes, there are obvious frequency-dependent out-of-phaseχm' signals below 3.5 K, along with a clear frequency-dependent decrease in the in-phaseχm'signals, suggesting the SMM behavior of these complexes at low temperature.The trans-[PPh3(PhCH2)][Ru(acac)2(CN)2] has been employed firstly to synthesize cyanide-bridged complexes, and two cyanide-bridged alternated 1:1 RuⅢ-MnⅢcomplexes structurally characterized as single chain containing co-crystallized bulk anions and cations have been successfully assembled from the reaction of this cyanide precursor and [Mn(TPP)(H2O)2]+. Systematic investigation over their magnetic properties reveals the typical single-chain magnet (SCM) behaviors for both of them. To the best of our knowledge, this is the first example of heterobimetallic porphyrin-based SCM.2. A series of seven new cyanide-bridged heterometallic complexes including two tetranuclear FeⅢMnⅢ3 compounds, two heptanuclear MⅢMnⅢ6 (M= Fe, Cr) compounds, and three two-dimensional M-MnⅢ(M= FeⅢ, CrⅢ, CrⅠ) networks have been successfully assembled from four polycyanidemetalates containing five or six cyanide groups and two manganese(Ⅲ) building blocks containing bicompartimental Schiff base ligands. All the complexes have been characterized by element analysis, IR spectra and X-ray diffraction. Single structure analysis reveal that the structure of the tetranuclear FeⅢMnⅢ3 complexes can be characterized as "T"-like, while the structure of the two heptanuclear ones are cage-shaped. The structural difference between these complexes demonstrates the effect of the number of charge and cyanide groups of polycyanidemetlates as well as the position and size of substituted group at the Schiff base ligand on the structure of cyanide-bridged heterometallic complexes. It is worth noting that the cyanide-bridged polynuclear complexes are self-complementary through coordinated aqua ligand from one complex and the free O4 compartment from the neighboring complex, giving supramolecular one-dimensional ladders and three-dimensional networks. Investigation over magnetic properties of all the heterometallic complexes reveals the ferromagnetic interaction between MnⅢand FeⅢmagnetic centers and antiferromagnetic coupling between MnⅢand CrⅢor CrⅠions. Due to the relatively strong intermolecular hydrogen bond interactions, the several polynuclear cyanide-bridged complexes show some characters of metamagnet behavior at low temperature. The three complexes with two-dimensional structure exhibit three-dimensional antiferromagnetic ordering with typical metamagnetic behavior at low temperature. 3. Two mononuclear seven-coordinated macrocycle manganese(Ⅱ) compounds and five dicyanide-containing precursors have been employed as building blocks to assemble cyanide-bridged heterobimetallic complexes, resulting in nine new cyanide-bridged FeⅢ-MnⅡ, AgⅠ-MnⅡand AuⅠ-MnⅡsingle chain complexes. All the complexes have been characterized by element analysis, IR spectra and X-ray diffraction. Single X-ray diffraction analysis reveals their one-dimensional single cyanide-bridged cationic polymeric chain structure consisting of alternating units of [Mn(L)]2+(L represents the fifteen-membered ring ligands) and [Fe(L')(CN)2]" (L'= bpb2-, bpClb2- or bpdBrb2-) or [Ag/Au(CN)2]- with free CIO4- or [Ag/Au(CN)2]- as balanced anion. Investigation over magnetic properties of these five one-dimensional single chain cyanide-bridged FeⅢ-MnⅡcomplexes reveals the antiferromagnetic magnetic coupling between neighboring FeⅢand Mn" ions through the bridging cyanide group, while very weak antiferromagntic interaction can be found between the MnⅡions bridged by [Ag/Au(CN)2]-in the cyanide-bridged AgⅠ-MnⅡand AuⅠ-MnⅡcomplexes.4. A new cyanide-containing precursor trans-K[Fe(salen)(CN)2]CH3OH (1) has been designed, synthesized and structurally characterized. Two cyanide-bridged trinuclear FeⅢ2MnⅡcomplexes and two one-dimensional cyanide-bridged FeⅢ-Mn" complexes have been successfully assembled from compound 1 and Mn(bipy)Cl2, Mn(phen)2Cl2 or two mononuclear seven-coordinated macrocycle manganeseⅡcompounds. All the complexes have been characterized by element analysis, IR spectra and X-ray diffraction. The structural difference between these complexes reveals that the macrocycle manganese(Ⅱ) compounds are facile for forming one-dimensional complexes, while other organic ligands with large steric volume, such as bipy and phen, are more prone to construct polynuclear complexes. Investigation over magnetic properties of these heterometallic cyanide-bridged FeⅢ-MnⅡcomplexes reveals the overall antiferromagnetic interaction between neighboring FeⅢand MnⅡions through the bridging cyanide group. Four cyanide-bridged trinuclear FeⅢ-MnⅡ-FeⅢcomplexes have been obtained by the reactions of trans-K[Fe(bpb)(CN)2],trans-K[Fe(bpmb)(CN)2], trans-K[Fe(bpClb)(CN)2] and [Mn(acac)2]ClO4. The antiferromagnetic coupling nature between the cyanide-bridged FeⅢion and Mn" ion in these complexes has been found.In this dissertation, eighteen cyanide-containing building blocks have been employed to react with manganese(III)-porphyrin compounds, manganese(III)-Schiff-base compounds, seven-coordinated macrocycle manganese(II) compounds and other manganese(II) compounds, and over forty cyanide-bridged complexes with different structures, including molecular clusters, one-dimensional chain, and two-dimensional network, were successfully synthesized, which have been characterized by element analysis, IR spectra and X-ray diffraction. The magnetic properties of all the complexes have been studied in detail. The results of this dissertation can afford lots of valuable experiment gists and research ideas for the further investigation of the synthesis of cyanide-bridged complexes with novel structural types and the rational design and synthesis of interesting molecular-based magnetic materials, such as SMM and SCM.