Tuning the Structure and the Magnetic Properties of Metallo-supramolecular Polyelectrolyte−Amphiphile Complexes

Abstract

Self-assembly of Fe(2+) ions and the rigid ditopic ligand 1,4-bis(2,2':6',2''-terpyridin-4'-yl)benzene results in metallo-supramolecular coordination polyelectrolytes (MEPE). Sequential self-assembly of MEPE and dialkyl phosphoric acid esters of varying chain length via electrostatic interactions leads to the corresponding polyelectrolyte-amphiphile complexes (PAC), which have liquid-crystalline properties. The PACs have a stratified architecture where the MEPE is embedded in between the amphiphile layers. Upon heating above room temperature, the PACs show either a reversible or an irreversible spin-crossover (SCO) in a temperature range from 360 to 460 K depending on the architecture of the amphiphilic matrix. As the number of amphiphiles per metal ion is increased in the sequence 1:2, 1:4, and 1:6, the temperature of the SCO is shifted to higher values whereas the amphiphile chain length does not have a significant impact on the SCO temperature. In summary, we describe in this article how the structure and the magnetic response function of PACs can be tailored through the design of the ligand and the composition. To investigate the structure and the magnetic behavior, we use X-ray scattering, X-ray absorption spectroscopy, differential scanning calorimetry, faraday-balance, and superconducting quantum interference measurements in combination with molecular modeling.

Towards Mesostructured Zinc Imidazolate Frameworks

“…[33][34][35] It has been pointed out previously that the chemical shifts and peak widths of the different carbon atoms of the surfactant are a sensitive probe of the conformation of the template confined in inorganic hosts and host-guest interfacial interactions. [36,37] The 13 C signals of all MIFs show a downfield shift of the inner-chain methylene and terminal carbon of the surfactant chain (C4-C15 and C16/17, for labeling see the scheme in Figure 4) by about 1-2 ppm with respect to that typically found for CTAB molecules occluded in hexagonal mesostructures, and are consistent with those found for lamellar mesostructures. In particular, a chemical shift of the methylene carbons around d = 31 ppm has been assigned to a more mobile gauche-conformation found predominantly in hexagonal mesostructures, whereas a peak at about d = 33 ppm corresponds to a more rigid all-trans conformation, which is found in well-ordered lamellar morphologies.…”

“…The software package Materials Studio 5.5 (Accelrys) was used for setting up a suitable structural model. 13 C and 15 N solid-state cross polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) spectra were recorded at room temperature with a DSX Avance 500 FT spectrometer (Bruker) equipped with a commercial 4 mm MAS NMR double-resonance probe at a magnetic field of 11.7 T, the chemical shifts being referenced with respect to TMS ( Table S1 (Supporting Information). For transmission electron microscopy, samples were prepared by drop coating the solutions on Cu grids with lacey carbon backing (Plano GmbH).…”

“…These organic-inorganic hybrid architectures, which have been prepared, for example, from alkyl-A C H T U N G T R E N N U N G imidazolium surfactants and various metal salts, combine liquid-crystal templating with coordination chemistry, yet often at the expense of stable, highly condensed structures. [12,13] Recently, Ryoo et al have developed an interesting class of hierarchically micro-and mesoporous MFI zeolite nanosheets stacked into pillared arrays mediated by gemini-type surfactants. [14,15] Along similar lines, hierarchically porous silicates were obtained from layered zeolites pillared by arylic silsesquioxanes, thus generating multifunctional hybrid materials combining acidic and basic properties in the inorganic and organic compartments of the structure, respectively.…”

The Kinetics of Growth of Metallo‐supramolecular Polyelectrolytes in Solution

“…At near-stoichiometric amountso ft he reactants, we obtained high molar masses,w hich follow the order Ni-MEPE % Co-MEPE < Fe-MEPE. [27] Finally,M EPEs exhibit excellent electrochromic properties. The forwardp olymerization rate constants follow the order Co-MEPE < Fe-MEPE < Ni-MEPE and the growth of MEPEsc an be accelerated by adding potassium acetate.…”

Template Syntheses, Crystal Structures and Supramolecular Assembly of Hexaaza Macrocyclic Copper(II) Complexes

“…Supramolecules constructed from metal complexes have attracted great attention due to their structures 1,2 and potential applications such as in catalysis, [3][4][5][6] magnetism, [7][8][9] nonlinear optical behavior, 10,11 gas storage, 12,13 and molecular sensing, 14,15 etc. The metal complexes can be further extended by secondary interactions such as hydrogen bonding, 16 π-π, 17 C-H···π, 18 and C-H···O 19 interactions to form supramolecules.…”