| The coordination polymers constructed from the flexible multicarboxylate ligandshave received intense interest, mostly motivated by their intriguing variety ofarchitectures and potential properties in applications: gas storage, nonlinear optics,magnetism, chiral separation, catalysis, etc. In this work, we focus on two flexibleN-multicarboxylate ligands, imidazolium-N,N′-diacetate （HDAM） andN-（4-carboxyphenyl） iminodiacetic acid （H3CPIDA）, under a rational syntheticstrategy to design and synthesize a series of compounds with fascinating topologicalstructures and novel properties. We selected LnX3（Ln=La, Pr, Nd, Sm; X=ClO4, NO3,Cl） and HDAM in different solvents （H2O or H2O/DMF） under the same pH value atroom temperature to prepare compounds1–11. Under the similar condition,compounds12–15were obtained from HDAM and the transition metals Co（Ⅱ）, Cu（Ⅱ）,Zn（Ⅱ）, and Ag（I）. A new compound16was prepared by Bi（ⅡI） and HDAM at lowerpH value. With introducing the bpy ligand to the system, compounds17and18wereformed by HDAM and Co（Ⅱ）, Cd（Ⅱ）, respectively. Those compounds derived fromH3CPIDA were all obtained by hydrothermal synthesis. In compounds19–21,H3CPIDA ligands afford intriguing modes with Zn（Ⅱ）, Cd（Ⅱ）, and Pb（Ⅱ） to build thenovel structures. In the presence of bpy, bbi, and bix ligands, compounds22–28wereobtained from the H3CPIDA and the transition metals ions Co（Ⅱ）, Zn（Ⅱ）, and Cd（Ⅱ）,respectively.In1–18, DAM–ligands display14coordination modes μ1–μ5as trans-orcis-conformation, eight of them are firstly reported for the HDAM compounds.Compounds1and2both contain the same2D corrugated layers bridged by DAM–with different bridging modes, exhibiting tcs and （4,6）-connected topologies,respectively. The structural differences of1and2lie in the linkages of DAM–between the layers. Compound3also possesses a3D architecture with an ant net,which is pillared by2D （4,4） fan-shaped layers in a–ABAB–sequence. Compounds4–10contain the similar2D layers to1and2. The analogous cationic structures4–9show a4-connected sql net and10presents a （4,5）-connected network, resulting from the different modes of flag-like DAM–above and below the layers. Compound11with identical molecular formula with10, displays a2D double-layer, consisting of acouple of （4,4） rectangular gird layers, which exhibits a （3,6）-connected network.{[La（trans-DAM）（cis-DAM）（H2O）2]（ClO4）·3H2O}n1{[La2（trans-DAM）3（H2O）4]（OH）3·7H2O}n2{[La（trans-DAM）2（H2O）2]Cl·4H2O}n3{[Ln（trans-DAM）2（H2O）2]（ClO4）·3H2O}n, Ln=Pr, Nd, Sm4,6,8{[Ln（trans-DAM）2（H2O）2]（NO3）·3H2O}n, Ln=Pr, Nd, Sm5,7,9{[Nd（trans-DAM）（cis-DAM）（H2O）2]Cl·5H2O}n10{[Nd（trans-DAM）2（H2O）2]Cl·5H2O}n11[Co（cis-DAM）2（H2O）2]12{[Cu3（cis-DAM）4（H2O）2]（OH）2·5H2O}n13[Zn（trans-DAM）2]n14[Ag3（trans-DAM）2（NO3）]n15{[Bi（trans-DAM）（cis-DAM）（H2O）]（NO3）·H2O}n16{[Co（trans-DAM）（bipy）（H2O）2]（OH）·3H2O}n17{[Cd（trans-DAM）（bipy）（H2O）]（NO3）·2H2O}n18[Zn2（CPIDA）（OH）]n19)={[Cd3（CPIDA）2（H2O）4]·5H2O}n20{[Pb3（CPIDA）2（H2O）3]·H2O}n21{[Co3（CPIDA）2（bipy）3（H2O）4]·2H2O}n22[Zn2（HCPIDA）2（bipy）（H2O）4]·2H2O23[Cd（HCPIDA）（bipy）（H2O）]n24[Co3（CPIDA）2（bbi）2（H2O）2]n25[Cd3（CPIDA）2（bbi）（H2O）2]n26{[M6（CPIDA）4（bix）3]·10H2O}n, M=Co, Zn27,28The molecule of12contains two μ1-cis-DAM–and one Co（Ⅱ） ion. Compound13shows a2D chiral layer, which is formed by the left-hand chains from Cu ions andcis-DAM–. With Zn ions and μ2-trans-DAM–, compound14displays a brick wall-like2D layer. In15, NO3–also coordinate to Ag（I）, and connect the chains formed by theμ5-trans-DAM–as μ2-η0:η2, μ3-η1:η2modes and Ag（I）, to build an interesting3Dframework. With the same bis-μ1-η1:η1coordination modes, trans-DAM–andcis-DAM–link Bi（ⅡI） into16, displaying a2D （4,4） gird layer. With bipy ligand,compound17possesses a2D （4,4） gird layer with μ2-trans-DAM–. In18,μ3-trans-DAM–and bipy bridge Cd（Ⅱ） to construct a2D double-layer, consisting of acouple of （4,4） rectangular gird layers. The topological structures of the2D-layer13, 14,16and17all present a4-connected sql net. Compound18shows a（3,4）-connected2D double-layer network。In19–28, depending on the degree of deprotonation and the coordination of thenitrogen atom, H3CPIDA ligands provide10coordination modes （μ1, μ3–μ6）, eight ofthem are firstly reported for the H3CPIDA ligand. In19–24, CPIDA3–adopt the highercoordination number and more flexible coordination geometry, resulting from thelonger ionic radiis. In19, μ5-CPIDA3–bridge the Zn（Ⅱ） ions to form a3D frameworkwith a （3,4,5）-connected topological structure. Compound20adopts a2Ddouble-layer connected by μ5-CPIDA3–and Cd（Ⅱ）, which show a （4,5,6）-connectednetwork. Compound21shows a3D porous framework with μ5, μ6-CPIDA3–in ahead-to-tail mode. With the influence of rigid bpy ligands, it is very difficult to extendthe structures through the CPIDA3–. So, compounds22–24possess3D,0D and2Ddouble-layer, respectively, in which the rigid aromatic rings of CPIDA3–, HCPIDA2–and the bpy ligands stand vertically. The flexible lignds bbi and bix play a importantrole in the construction of the3D frameworks25–28, in which the carboxylate groupsof CPIDA3–are completely deprotonated. In25, cis-bbi link the double-layersconstructed from μ4-CPIDA3–and Co（Ⅱ） into a3D framework, which displays a（3,4）-connected topology. Compound26possesses （4,5）-connected3D topologicalstructure, which is extended by trans-bbi and the double-layers from μ5-CPIDA3–andCd（Ⅱ）. Compounds27and28feature the analogous structures. The trans-and cis-bixare firstly exhibiting at the same time and link the double-chains and double-layersformed by μ3, μ4-CPIDA3–, respectively, into novel3D porous frameworks.In these compounds, there are abundant hydrogen bonding and π···π stackinginteractions, which linke those lower dimensional compounds into3D supramolecularframeworks. The results imply that the design and synthesis of coordination polymersstill remains a great challenge. Clearly, the various coordination modes of DAM–areto a certain extent influenced by many factors, such as the coordination of metal ions,the metal/ligand ratios, counteranions, solvent preference, pH values and thetemperature, etc. those factors are co-working and play a subtle role in inducing theabundant coordination modes and conformations of flexible N-multicarboxylateligands and leading to the different topological structures.Based on the data from X-ray single-crystal diffraction, the structures andproperties have been characterized with the aid of elemental analysis, XRD, TGA,FTIR, UV-Vis DRIS, and fluorescence spectroscopy. The thermal stabilities of1–3,6, 11and21are outstanding and the frameworks are beginning to collapse after300°C.The two-dimensional correlation infrared spectroscopy （2D-IR COS） with thermaland magnetic perturbation, which we exploited and designed by ourselves, areintroduced into the coordination polymers derived from flexible N-multicarboxylateligands for the first time. It is should be noted that employing2D correlation analysisof FTIR, the hardly overlapped characteristic bands of groups in7,16and22can bedistinguished, depending on their different sensitivity to thermal and magneticperturbation. So it is meaningful to explore more function of generalized2Dcorrelation FTIR spectroscopy with various perturbation, such as magnetism, light,heat, electricity, chemistry, etc. Due to the interaction between magnetic particles, thepositive charged imidazolium and exoteric magnetic field,2D correlation analysis ofFTIR can probe the sensitive response of the groups coordinated to magnetic particles,which provide valuable information of the electromagnetic transformation at themolecular level. Compounds23and28show intense emission bands at500and430nm, respectively, upon350and314nm excitation and exhibit a quenching of thefluorescence with37.43and22.10ns at room temperature, which indicate they arepotential candidates on the fluorescent materials.The band structures, the total and partial density of states （DOS）, optical responsefunctions and the chemical bonding properties calculations based on the DFT methods（Density Functional Theory） of the cation frameworks of3,11and compounds7,15,18,21and26were carried out by using the computer code CASTEP （CambridgeSerial Total Energy Package）. We also compare the calculated results with theexperimental data. The band structures demonstrates compounds7,11,18and21possess the features of semiconductors, while the rest are insulators. Comparing to thecoordination modes of the ligands, we also analyzed the Mulliken charge of someatoms and the bond population of these compounds. Moreover, according to theoptical property analysis, we also obtain the theoretical absorption spectra andrefractive indexes. The anisotropy of theoretical refractive indexes of7、15、18、21and26suggest isotropy. |
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