This paper reports the synthesis, liquid crystal behavior, and charge-transport properties in the mesophase of isocyano-triphenylene gold, copper, palladium, and platinum complexes MX(CNR) (CNR = ...2-(6-(4-isocyanophenoxy)hexyloxy)-3,6,7,10,11-pentakisdodecyloxytriphenylene; M = Au, X = Cl, C6F5, C6F4OC10H21, CN; M = Cu, X = Cl), (μ-4,4′-C6F4C6F4){Au(CNR)}2, (μ-Cl2){Cu(CNR)2}2, and MX2(CNR)2 (M = Pd, Pt; X = Cl, Br, I, and M = Pt, X = CN). The thermal and electronic properties of these materials are modulated by the metal fragment. The complexes that display columnar mesomorphism are those that support more than one triphenylene per molecule or those that produce a similar effect by dipole–dipole interactions between the metal groups. These circumstances improve the balance of favorable enthalpic interactions versus unfavorable entropic contributions into a columnar stacking. Hybrid inorganic/organic dual columnar mesophases with high SCLC hole mobility along the columnar stacking, above 1 cm2 V–1 s–1, have been found. It is worth noting that the dicyanoplatinum complex displays mesophase phosphorescence based on Pt···Pt interactions.
Dendritic polyisocyanides can be considered as promising polytopic ligands to generate a great diversity of metallodendrimers due to the ability of the isocyanide moiety to bind to various transition ...metals. Here, new isocyanide-containing dendrimers and their corresponding polynuclear gold complexes have been prepared, G i (NC) Z and G i (NCAuR) Z , respectively, where G i is a poly(phenyl ether) dendrimer, i is the generation number (i = 0, 1, or 2), Z is the number of peripheral groups (Z = 3 × 2 i ), and AuR are the surface groups (R = Cl, C≡C-C6H4−OC12H25, C≡CC6H2(OC12H25)3. The compounds are derived from a highly flexible phenyl ether-based dendritic core, G i , having the general formula G0 = C6H3(OC11H22OC6H4-)3, G1 = C6H3OC11H22OC6H3(OC11H22OC6H4-)23, G2 = C6H3OC11H22OC6H3{OC11H22OC6H3(OC11H22OC6H4-)2}23), growing from the trivalent phloroglucinol and with undecylene aliphatic spacers between each branching benzene ring and end-functionalized by isocyanide groups. As in their monomeric model counterparts, stable liquid-crystalline phases are induced upon complexation of the AuR gold moieties at the branch termini. The nature of the anionic ligand R promotes the appearance of smectic or columnar mesophases, the formation of which are governed by steric and dipolar interactions. Based on X-ray diffraction experiments, models describing the supramolecular organization of these metallodendrimers into smectic and columnar mesophases are proposed: columnar phases result from the one-dimensional stacking of molecular disks made of self-assembled supermolecules in oblate cylindrical conformation, while the smectic phases form by the lateral two-dimensional registry of the supermolecules in antiparallel head-to-head prolate conformation.
Supramolecular mono‐ and dinuclear liquid‐crystalline gold(I) aggregates have been synthesized by means of hydrogen bond interactions of 2,4,6‐triarylamino‐1,3,5‐triazine with thiolate moities of ...gold metalloacids Au(PR3)(SC6H4COOH) or μ‐(binap){Au(SC6H4COOH)}2, in 1:1 and 2:1 molar ratio, respectively. All of the supramolecular aggregates display a stable columnar hexagonal mesophase (Colh) at room‐temperature. The supramolecular arrangement within the columns consists of the one‐dimensional stacking of triazine units, with the core of the attached metallic thioacid fragments acting as the fourth branch. The phosphine‐containing moieties of the metallic thioacid protrude out in the aliphatic continuum. These complexes do not show metallophilic interactions, but this strategy appears very promising for the future design of room‐temperature LC mesophases containing interacting metallic fragments.
Golden get‐together: Mono‐ and dinuclear aggregates form by hydrogen bonding between triazine units (see figure; green) and thiolate groups on aryl phosphine–gold(I) metalloacids (blue). These aggregates form stable columnar mesophases at room temperature. The metal fragments act as a wedge between the columnar stacking of triazine discogens.
Rodlike gold(I) complexes, Au(C6F4OCmH2m+1)(CNC6H4C6H4OCnH2n+1) (m=2, n=4, 10; m=6, n=10; m=10, n=6, 10), display interesting features. They are liquid crystals and show photoluminescence in the ...mesophase, as well as in the solid state and in solution. The single‐crystal, X‐ray diffraction structure of Au(C6F4OC2H5)(CNC6H4C6H4OC4H9) confirms its rodlike structure, with a linear coordination around the gold atom, and reveals the absence of any Au⋅⋅⋅Au interactions (such interactions are often present in luminescent gold complexes). Well‐defined, intermolecular Fortho⋅⋅⋅Fmeta interactions, with remarkably short intermolecular F⋅⋅⋅F distances (2.66 Å), are observed; these interactions seem to be responsible for the crystal packing, which consists of an antiparallel arrangement of molecules. Experiments under different conditions support the explanation that the photoluminescence has an intramolecular origin.
Luminescent liquid gold! Stable mesomorphic tetrafluorophenylgold(I) biphenylisocyanide complexes display strong luminescence in the smectic C mesophase, in the solid state, and in solution (see figure). These complexes show good mesophase stabilization without gold–gold interactions in the solid state, and display remarkably short intermolecular fluorine–fluorine interactions in the solid state.
This study reports new carbene azulene gold(I) complexes AuCl{C(NHAz)(NR2)} (R = Me (1) and nBu (2)) and Au(C6F4OC10H21){C(NHAz)(NR2)} (R = Me (3) and nBu (4)) prepared by reaction of ...2-isocyanoazulene gold(I) complexes AuX(CNAz) (X = Cl and C6F4OC10H21) with the corresponding secondary amines. Their photophysical properties were investigated by absorption and emission spectroscopies, and by TD-DFT calculations. All the compounds display an intense coloration based on HOMO-LUMO transitions, dominated by the azulene core. Gold-isocyanide complexes show a slight bathochromic shift related to azulene, while a hypsochromic shift was observed after formation of carbene complexes. Thus, the transformation of the gold-isocyanide group into the gold-carbene functionality produces a substantial color change from blue to deep purple. This different electronic behavior is mainly due to the stabilization of the LUMO orbital in the isocyanide complexes, and to the stabilization of the HOMO in the carbene derivatives. These carbene gold complexes show fluorescence in solution associated with the azulene core. This work illustrates how the synthetically easy isocyanide-carbene transformation open new perspectives to a fine color modulation in organometallic azulene dyes.
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•Strongly purple colored carbene azulene gold compounds are prepared.•They show a hypsochromic shift related to the starting isocyanide complexes and azulene itself.•The spectral shift is mainly related to the stabilization of the HOMO orbital energy levels.•The carbene-gold fragment acts as an electron-donating substituent of the azulene core.•All of them are slightly fluorescent dyes.
Gold, palladium and platinum complexes with an unusual isocyanide ligand containing a carboxylic acid function, AuCl(CNC(6)H(4)COOH), cis-MI(2)(CNC(6)H(4)COOH)(2) and trans-MI(2)(CNC(6)H(4)COOH)(2) ...(M = Pd, Pt) have been isolated. The carboxylic acid group of the coordinated isocyanide acts as a hydrogen donor for hydrogen-bonding and three series of stable hydrogen-bonded liquid crystalline metal complexes have been prepared with decyloxystilbazole. Although all the metal acid derivatives used are not mesomorphic, and decyloxystilbazole only shows an ordered Smectic E phase, four out of the five hydrogen-bonded decyloxystilbazole complexes studied display enantiotropic smectic A or nematic mesophases. The single crystal X-ray diffraction structure of trans-PdI(2)(CNC(6)H(4)COOH)(2).C(4)H(8)O(2) has been determined and confirms the formation of a supramolecular array in the solid state supported by hydrogen-bonding.
In this work, the first experimental results of thermotropic liquid crystals used as phase change materials for thermal storage are presented. For that purpose, the n = 10 derivative from the family ...of 4′-n-alkoxybiphenyl-4-carboxylic acids has been prepared. Different techniques like polarized-light microscopy, differential scanning calorimetry, thermogravimetric analysis and rheological measurements have been applied for its characterization. Having a mesophase/isotropic transition temperature around 251 °C, a clearing enthalpy of 55 kJ/kg, a thermal heat capacity of around 2.4 kJ/kg and a dynamic viscosity lower than 0.6 Pas, this compound fulfills the main requirements for being considered as latent heat storage material. Although further studies on thermal stability are necessary, the results already obtained are both promising and encouraging since they demonstrate de viability of this new application of liquid crystals as thermal storage media.
Stable and structurally simple chiral tetrafluorophenyl-gold(I) isocyanide complexes Au(C6F4OR1)(C⋮NC6H4C6H4OR2) R1 = (R)-2-butyl, R2 = C n H2 n +1 (n = 2, 10); R1 = C m H2 m +1 (m = 2, 10), R2 = ...(R)-2-butyl; R1 = R2 = (R)-2-butyl displaying a twist-grain boundary phase (TGBA*) and blue phases are described. Their mesogenic behavior is discussed and their thermal properties are easily tuned by changing the number and position of the chiral chain in the complexes.
This work reports an uncommon modulation of columnar segregation of metal–organic triphenylene liquid crystals by blending two structurally dissimilar metallomesogens that can self-associate through ...complementary electron donor–acceptor interactions. The constituent molecules are cis-PtCl2(CNR)2 (CNR = 2-(6-(4-isocyanophenoxy)hexyloxy)-3,6,7,10,11-pentakisdodecyloxytriphenylene) that displays an organic/inorganic segregated columnar mesophase and PtCl2(Bipy) (Bipy = didodecyl 2,2′-bipyridyl-4,4′-dicarboxylate) that shows a lamellar mesomorphism. The phase diagram of this system was constructed using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray scattering data. The phase diagram corresponds to a typical binary system with an intermediate compound (in this case a supramolecular aggregate) of stoichiometry PtCl2(CNR)2/2PtCl2(Bipy), which is maintained in solution. This species shows an unusual columnar mesophase formed by the stacking of alternating organic/inorganic fragments. Quantum chemical calculations show that the columnar structure is mainly supported by complementary π electron donor–acceptor interactions between each triphenylene group of the isocyanide complex and a platinum-bipyridine molecule. This induces the elimination of the organic/inorganic columnar segregation of the isocyano parent component and constitutes an unconventional example of modulation of organic/inorganic segregation in columnar mesophases by the intercalation of metal complexes into hexaalkoxytriphenylene stacks.
This manuscript reports the synthesis and liquid crystal behavior of isocyanoazulene gold(I) complexes AuX (CN-Az) (Az = azulene; X = halide, perhalophenyl or alkynyl) and ...μ-4,4′-C6F4C6F4{Au(CN-Az)}2. The comparison of the X-ray structures of homologous compounds, reveals that the introduction of a long substituent in the system produces a loss of molecular planarity that induces a decrease in the melting temperatures. The free 2-isocyanoazulene is not a liquid crystal itself, but its gold complexes bearing a C10 hydrocarbon chain display a SmA mesophase, whose formation is driven by nanosegregation between molten chains and aromatic parts. The free isocyanide is strongly colored and displays fluorescence in solution associated with the azulene fragment, which is largely diminished upon coordination to the gold fragment.
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•Strongly colored 2-isocyanoazulene gold(I) complexes have been synthesized.•The gold complexes bearing a C10 hydrocarbon chain display a SmA mesophase.•The emission of the isocyanide ligand is partially quenched by the gold fragment.
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