Syntheses, Structures And Magnetic Properties Of Coordination Polymers With Flexible Zwitterionic Dicarboxylate As Coligands

Metal-organic coordination polymers are currently of great interest, not only for their potential applications such as nonlinear optics, magnetism, porosity, chemical sensing and catalysis, but also for the fundamental scientific issues such as their intriguing topological variety and the physical laws underlying the assembling processes. To design and prepare novel coordination compounds, discover new magnetic phenomena, and investigate the magneto-structural correlation, using azide or cyanate ions as short ligands, in combination with the use of a series of flexible zwitterionic carboxylate coligands, a series of new coordination polymers have been prepared; Simultaneously, using the rigid or flexible aromatic dicarboxylate bridging ligands between transition metal ions, in combination with the use of the terminal or neutral auxiliary bridging ligands, some new coordination polymers have also been prepared. All these compounds have been structurally characterized; and some of them have been magnetically characterized. This dissertation covers the following parts:(1) Syntheses, structures and magnetic properties of transition metal-azide coordination compounds with flexible zwitterionic dicarboxylate as coligandsHere, we report the syntheses, structures and magnetic properties of eleven transition metal-azide coordination compounds with flexible zwitterionic dicarboxylate coligands of different lengths (4,4'-trimethylenedipyridinio-N,N'-diacetate,4,4'-dipyridinio-N,N'-diacetate and 1,2-bis(N-carboxymethyl-4-pyridinio)ethane), and investigate the magneto-structural correlation.(i) Using azide ions as short ligand, in combination with the use of the flexible zwitterionic carboxylate coligands 4,4'-trimethylenedipyridinio-N,N'-diacetate (bcpp) and 1,2-bis(N-carboxymethyl-4-pyridinio)ethane (bcpe), seven new coordination polymers [M2(bcpp)(N3)4]n (M=Mn,1; Co,2; and Ni,3),[M2(bcpe)(N3)4]n(M=Mn,8; Co,9; and Ni,10) and {[Cu3(bcpe)(N3)6]·2H2O}n (11) have been prepared. Compound 1-3 and 8-10 are isomorphic and consist of 2D coordination networks in which uniform chains with triple bridges (N3)2(COO) are cross-linked by the flexible 4,4'-bipyridine-based spacers, while compound 11 also consists of two-dimensional coordination layers in which CuⅡchains are interlinked by the organic spacers, but the chain has mixedμ2-EO-azide,μ3-EO-azide andμ2-Ocarboxylate bridges and features tetranuclear dicubane-based units sharing Cu ions or alternatively linear trinuclear units connected by long axial Cu-N/O bonds. Magnetic studies reveal that the mixed (μ-EO-N3)(μ-COO)2 triple bridges transmit ferromagnetic coupling in the CoⅡand NiⅡcompounds, and the overall antiferromagnetic interactions exist in the MnⅡcompound; the CuⅡions linked by the equatorial-equatorial bridges within the units, which transmit strong ferromagnetic coupling, while very weak antiferromagnetic interactions through the equatorial-axial bridges between the units.(ii) Using azide ions as short ligand, in combination with the use of the flexible zwitterionic carboxylate coligand 4,4'-dipyridinio- N,N'-diacetate (bcp), four new coordination polymers [Mn3(bcp)(N3)6(H2O)2]n (4) {[Mn3(bcp)2(N3)2(SO4)2(H2O)4]·6H2O}n (5),{[Mn4(bcp)2(N3)8(H2O)2]·4H2O}n (6)和[Co3(bcp)(N3)6(H2O)2]n (7) have been prepared. Compounds 4 and 5 contain alternating chains with triple (N3)2(COO) and double ((N3)2) bridges, while compounds 6 and 7 contain the anionic tri- or tetranuclear units which are linked into coordination chains by the cationic bipyridinium spacers. Magnetic studies reveal that the triple bridge transmits AF coupling in the MnⅡcompounds, and a spin canting is observed in 5. The [(EO-N3)2] bridge in 6, with Mn-N-Mn =96.6°, also transmits antiferromagnetic coupling, providing the first example in the antiferromagnetic regime predicted theoretically for double EO azide bridges between MnⅡions.(iii) Here we report the first compound containing homoleptic 2D Mn-azide layers {(MV)[Mn(N3)4]}n (12), where MV2+ (methylviologen dication) is generated in situ reaction. The MV2+ cations are intercalated between the inorganic layers. Magnetic studies reveal that the symmetric feature of the structure precludes the possibility of spin canting in this compound.(2) Syntheses, structures and spectra properties of transition metal-thiocyanate coordination compounds with 1,4-diazoniabicyclo[2.2.2]octane-1,4-diacetate as coligandsWe have described the supramolecular architectures formed through the first- or second-sphere coordination between 1,4-diazoniabicyclo[2.2.2]octane-1,4-diacetate and different divalent metal ions. They are formulated as [Ni(SCN)2(H2O)4](L)2(H2O)2 (13), [M(SCN)2(H2O)8](L)2(H2O)4 (M=Co (14) and Mn (15) and [Zn(L)(SCN)2] (16).(3) Syntheses, structures and magnetic properties of transition metal-isocyanate coordination compounds with flexible zwitterionic dicarboxylate as coligandsUsing two zwitterionic dicarboxylate coligands 4,4'-trimethylenedipyridinio-N,N'-diacetate (bcpp) and 4,4'-dipyridinio-N,N'-diacetate (bcp), we obtained two new MnⅡ-isocyanate coordination polymers [Mn2(bcpp)(NCO)4]n (17) and [Mn2(bcp)(NCO)4]n (18). Magnetic studies revealed antiferromagnetic interactions through the (NCO)2(COO) triple bridges are stronger than those through the isoelectronic analogue (N3)2(COO), and quantum chemical calculations were performed upon these mixed bridging systems.(4) Syntheses, structures and magnetic properties of transition metal-azide coordination compounds with flexible zwitterionic monocarboxylate as coligandsUsing azide ions as short ligand, in combination with the use of the monocarboxylate 4,4'-dipyridinio-N,N'-diacetate coligand bearing both carboxylate and pyridine groups, five new coordination polymers {[Co2(L1)2(N3)4(H2O)]·4H2O}n (19),{[Mn6(L1)4(N3)12(H2O)]·5H2O}n (20) {[Cu2(L1)2(N3)3]·NO3}n (21),{[Cu4(L1)4(N3)2(O)]4(ClO4)·3(H2O)}n (22) and [Cu7(L2)2(N3)14]n (23) have been prepared. Compounds 19 and 21 are isomorphic and consist of 1D coordination chains built of dinuclear motifs with mixed (μ-EO-N3)(u-COO)2 triple bridges, while compounds 20 and 22 exhibit complicated 3D architecture, and compound 23 exhibits a novel 2D network. Magnetic studies reveal that domain ferromagnetic interactions exist in compounds 19 and 22, the overall antiferromagnetic interactions exist in compounds 20 and 21.In addition, using the aromatic dicarboxylate bridging ligands between transition metal ions, in combination with the use of the terminal or neutral auxiliary bridging ligands, some new coordination polymers have been prepared.(i) Transition metal coordination compounds with regid trans-stilbene-4,4'-dicarboxylic acid bridging ligandTo further explore the effect of the monodentate terminal ligands on the structure, we present here the syntheses and characterizations of two MⅡ-STDC-py (H2STDC=trans-stilbene-4,4'-dicarboxylic acid) coordination polymers with different metal ions:[Cu(STDC)(H2O)(py)2]-2py (24) and [Ni2(STDC)2(py)4(H2O)]·py·0.5H2O (25). Compound 24 consists of quasilinear chains, while 25 exhibits five-fold interpenetration of 3D diamond networks. The thermal stability and the guest absorption/desorption properties of 25 have been investigated.(ii) Syntheses, structures and magnetic properties of transition metal coordination compounds withα,α'-dihydroxy-bibenzyl-4,4'-dicarboxylate ligandWe herein report five metal-organic coordination polymers derived from different transition metal ions and the dicarboxylate ligandα,α'-dihydroxy-bibenzyl-4,4'-dicarboxylic acid (H2DHBBDC), which has additional functional sites (two hydroxyl groups) for potential metal coordination or hydrogen bonding. They are formulated as [M(DHBBDC)(H2O)4]·2H2O (M= Co (26), M=Mn (27), M= Ni (28) and M= Zn (29)) and [Zn3(OH)2(DHBBDC)2(bpy)(H2O)2]·2H2O (bpy=4,4'-bipyridine) (30). Compounds 26-29 are isomorphic and consist of 1D coordination chains in which metal ions are linked by the long dicarboxylate ligands, while compound 30 consists of 2D coordination networks with a novel entanglement topology having both polyrotaxane and polycatenane features. Magnetic studies on NiⅡand CoⅡcompounds reveal that the triple O-H…O hydrogen bonding bridges in compounds 26 and 28 transmit ferromagnetic coupling.