The Design, Synthesis And Magnetic Properties Of Novel Aromatic Hetero-Cyclic Polymers And Their Metal Complexes

The development of magneto-, opto- and electro multifunctional polymers have achieved highly attentions. Organic and polymeric magnets have received considerable interests due to their potential applications. The design and synthesis of novel organic magnetic materials, specially the preparation of multifunctional magnetic materials, have become a research focus.Four novel aromatic hetero-cyclic polymers and their corresponding metal complexes are designed and synthesized in this paper, and the magnetic behaviors of these complexes were studies. The aim is quest for the relationship of the structure of polymer, the kinds of metal ions and the magnetic properties of the corresponding complexes via synthesis of various structures of magnetic materials.Two kinds of polymers, the main-chain form and the side-chain form, have mainly prepared in the paper. The carbazole-containing polymer (PBTCA) was synthesized by polycondensation of 2,2'-diamino-4,4'-bithiazole (DABT) and N-(2-ethylhexyl)-3,6-diformylcarbazole (NDC). Two novel conjugated polymers containing symmetrical long side group (PPHBT and PPHPHN) were obtained by reacting bisdecyloxyterephthaldehyde (BDTA) with DABT and 5,6-diamino-l,10-phenanthroline (DAPH), respectively. The rigid conjugated (PDBT) and the . rigid non-conjugated polymers (PDPE) were prepared by 1,10-phenanthroline-5,6-dione (PD) with DABT and 4,4'-diaminodiphenyl ether (DAPE), respectively. The comb-like Copolymers (BIMT and PMB) comprised of N-2-thiazolylmetaacrylamide (NTMA) and 2-(1-butylimidazolium-3-yl) ethyl methacrylate tetrafluoroborate (BIMA) were prepared by free radical polymerization and reversible addtion-fragmentation chain transfer (RAFT) polymerization. And the metal complexes of these polymers were prepared. The structures of the polymers and the complexes were determined by FT-IR, ¹H NMR and element analysis. The metal contents were measured by complexometric titration and inductively coupled plasma emission spectrometer (ICP). The magnetic properties of these complexes were examined as a function of magnetic field strength at 4 K and as a function of temperature (4-300 K) at magnetic field strength of 30 kOe with a physical properties measurement system (PPMS) magnetometer. PBTCA-Nd³⁺ exhibits special soft ferromagnetism, it has a magnetic switch appears at about 15 K. When the temperature is less than 15 K, the PBTCA-Nd³⁺ complex is a ferromagnet, otherwise, it is a diamagnet. Both PPHBT-Nd³⁺ and PPHPHN-Nd³⁺ exhibit the characteristic of soft-magnetic materials at low temperature, the Curie-Weiss temperature are 80 K and 150 K, respectively. And the magnetic properties of PDBT-Fe²⁺, PDBT-Ni²⁺, PDPE-Fe²⁺ and PDPE-Ni²⁺ were studied. The Curie-Weiss temperature of ferrous complexes PDBT-Fe²⁺ and PDPE-Fe²⁺ are -81 K and -49 K, respectively. They are antiferromagnet. The falcial complexes PDBT-Ni²⁺ and PDPE-Ni²⁺ are ferromagnets, follow the Curie-Weiss relationship in the range of 200-300 K, with the Curie-Weiss temperature 62 K and 56 K, respectively.By comparing the magnetic properties of the six metal complexes BIMT-Ni, BIMT-Nd, BIMT-Nd-Ni, PMB-Ni, PMB-Nd and PMB-Nd-Ni, the bimetallic complexes show the best relatively saturated magnetization in all of the complexes. For the random polymeric complexes, both BIMT-Ni and BIMT-Nd show significant transition at about 240 K and 292 K, respectively. The BIMT-Nd-Ni solid exhibits ferromagnetic property, and its Curie-Weiss temperature is 12 K, while the DMSO solution of BIMT-Nd-Ni has a magnetic transtion at 150 K. As for the block polymeric complexes, PMB-Ni and PMB-Nd-Ni show the characteristic of antiferromagnet, which have the Curie-Weiss temperature -15 K and -28 K, respectively. And PMB-Nd exhibits the property of ferromagnet, with Curie-Weiss temperature 175 K.