Tetraphenylbenzosilole: An AIE Building Block for Deep-Blue Emitters with High Performance in Nondoped Spin-Coating OLEDs.

1,1,2,3,4,5-Hexaphenylsilole (HPS) is a star building block of aggregation-induced emission luminogens (AIEgens) in constructing OLED emitters. However, their development is obstructed by their complicated preparation and difficulty of achieving blue/deep-blue emission via structure modification and tuning. In this study, a benzo-group modification strategy was adopted to increase the skeleton rigidity and reduce the vibrational-rotational motion of peripheral substituted phenyl groups. The resulting building block, named tetraphenylbenzosilole (TPBS), was synthesized easily via a silyl radical cascade process with intermolecular radical cyclization. After the structure of the reaction substrate was tuned, four TPBS-based derivatives were obtained which not only inherited AIE characteristics from HPS but also exhibited high-efficiency deep-blue emission in the aggregated state thanks to their tuned HOMOs/LUMOs. Similar to HPS, propeller-like conformations in their single crystals were observed. In nondoped spin-coating OLEDs, these AIEgens all exhibited satisfactory performance with high EQEs (3.1-3.6%) at CIE coordinates of (0.15, 0.10), the best result reported so far for spin-coating-type AIEgens in blue nondoped OLEDs. All of the data showed the feasibility of our strategy for solving the shortage of AIEgens serving as building blocks for deep-blue emitters. We foresee the development of systems based on TPBS or its derivative materials inspired by this work.

Selective Cu(ii) sensing by a versatile AIE cyanostilbene-based gel system.

Cyanostilbene-based derivatives 1-3 were designed, synthesized and fully characterized. By screening their gelating abilities, we observed that the subtle difference in the position of the pyridine nitrogen greatly affected the resulting fluorescence and gelation properties. Notably, 1 was found to be a versatile ambidextrous gelator capable of forming organo-, hydro-, and Cu(ii) specific metallogels. Furthermore, a rare organogel-to-metallogel transformation at room temperature was also observed upon exposure of the 1-DMSO/H2O gel to aqueous Cu(ii). This process, accompanied by colour and fluorescence changes, provides an effective strategy for the preparation of novel sensing soft materials.

Self-Complementary Dimers of Oxalamide-Functionalized Resorcinarene Tetrabenzoxazines.

Self-complementarity is a useful concept in supramolecular chemistry, molecular biology and polymeric systems. Two resorcinarene tetrabenzoxazines decorated with four oxalamide groups were synthesized and characterized. The oxalamide groups possessed self-complementary hydrogen bonding sites between the carbonyls and amide groups. The self-complementary nature of the oxalamide groups resulted in self-included dimeric assemblies. The hydrogen bonding interactions within the tetrabenzoxazines gave rise to the formation of dimers, which were confirmed by single-crystal X-ray diffractions analysis and supported by NMR spectroscopy and mass spectrometry. The self-included dimers were connected by numerous and strong intermolecular N-H⋅⋅⋅O and C-H⋅⋅⋅O hydrogen bonds supplemented with C-H⋅⋅⋅π interactions, forming one-dimensional polymers, which were then further linked into three-dimensional networks.

Magnetostructural Characterization of Oxalamide Dihalo-Bridged Copper Dimers: Intra- and Interdimer Interactions Studied by Single-Crystal Electron Spin Resonance Spectroscopy.

Detailed single-crystal electron spin resonance (ESR) analysis of oxalamide complexes with halogen-bridged copper dimers, supported by X-ray, magnetic susceptibility, and powder ESR studies, is reported. Four complexes with two different ligands are synthesized: [CuLA (µ-X)]2 and [CuLV (µ-X)]2 , for which LA =N-(l-alanine methyl ester)-N'-[(2-pyridine-2-yl)methyl]oxalamide and LV =N-(l-valine methyl ester)-N'-[(2-pyridine-2-yl)methyl]oxalamide, for which X=Cl or Br. X-ray analysis shows that the geometry at each copper(II) ion is square pyramidal, whereas two pyramids share one base-to-apex edge with parallel basal planes. The complexes are linked by hydrogen bonds into infinite chains and are further linked into a 3D network. Susceptibility measurements show that the copper centers in the dimers are weakly antiferromagnetically coupled (|J|≈1-2 cm-1 ). From powder ESR spectroscopy, the g values and dx2-y2 orbital as the ground state of the unpaired electron are determined. The complexes show unusual anisotropic splitting and merging of the ESR lines if their single crystals rotate in a magnetic field. The observation of this partially resolved intradimer dipolar splitting enables estimation of the weak interdimer exchange interaction parameter |J'|≈0.001 cm-1 .

Cu(II)-specific metallogel formation by an amido-anthraquinone-pyridyloxalamide ligand in DMSO-water.

This study on the CuCl2-induced and water-mediated metallogel formation by a pyridine containing anthraquinone-based ligand in DMSO provides significant insights on the relationship between the coordination geometry and metallo-gelation aptitude for a series of variably substituted pyridyloxalamide ligands.

Crystal structures and magnetic properties of a set of dihalo-bridged oxalamidato copper(II) dimers.

A set of four copper(ii) complexes, and (X = Cl, Br; = N-(l-leucine methyl ester)-N'-((2-pyridin-2-yl)methyl)oxalamide and = N-benzyl-N'-((2-pyridin-2-yl)methyl)oxalamide), have been synthesized and characterized by X-ray structural analysis, electron paramagnetic resonance (EPR) spectroscopy on single crystals and by SQUID magnetization measurements. X-ray diffraction studies show one-dimensional hydrogen bonded networks of dimeric copper(ii)-complexes bridged by two halide ions and with the two metal centers 3.44-3.69 Šapart. The geometry at each copper(ii) atom is ideal or near ideal square pyramidal. EPR and SQUID studies indicate that all complexes exhibit weak antiferromagnetic interactions between the Cu(ii) paramagnetic centers, with exchange parameter |J| ∼ 1 cm(-1). Magneto-structural comparisons among similar dihalo-bridged Cu(ii) dinuclear complexes are also provided, and a possible correlation has been established.

New frontiers in hybrid materials: noble metal nanoparticles--supramolecular gel systems.

The last decade has witnessed an increasing interest in the development of hybrid materials with novel properties. Noble metal NPs-gel materials represent a new class of hybrid composites, envisaged by many to have great potential for technological applications, as a consequence of the beneficial integration of the properties of both the NPs and the gelling compounds. This review article provides an up-to-date account of the most interesting and inspiring works published in the field, especially focusing on their preparation and characterization. Some examples of practical uses of such intriguing materials are also described.

Preparation of potentially porous, chiral organometallic materials through spontaneous resolution of pincer palladium conformers.

Understanding the mechanism by which advanced materials assemble is essential for the design of new materials with desired properties. Here, we report a method to form chiral, potentially porous materials through spontaneous resolution of conformers of a PCP pincer palladium complex ({2,6-bis[(di-t-butylphosphino)methyl]phenyl}palladium(II)halide). The crystallisation is controlled by weak hydrogen bonding giving rise to chiral qtz-nets and channel structures, as shown by 16 such crystal structures for X = Cl and Br with various solvents like pentane and bromobutane. The fourth ligand (in addition to the pincer ligand) on palladium plays a crucial role; the chloride and the bromide primarily form hexagonal crystals with large 1D channels, whereas the iodide (presumably due to its inferior hydrogen bonding capacity) forms monoclinic crystals without channels. The hexagonal channels are completely hydrophobic and filled with disordered solvent molecules. Upon heating, loss of the solvent occurs and the hexagonal crystals transform into other non-porous polymorphs. Also by introducing a strong acid, the crystallisation process can be directed to a different course, giving several different non-porous polymorphs. In conclusion, a number of rules can be formulated dictating the formation of hexagonal channel structures based on pincer palladium complexes. Such rules are important for a rational design of future self-assembling materials with applications in storage and molecular recognition.

The formation of CuCl2-specific metallogels of pyridyloxalamide derivatives in alcohols.

Isomeric pyridyloxalamide derivatives 1-3, which differed in the position of the nitrogen atom on the pyridyl ring, showed remarkably different gel-forming aptitudes in the presence of CuCl2 salt in alcohols. Whilst derivatives 1 and 3 formed a soluble complex and a solid precipitate, respectively, ligand 2 generated a remarkably metal- and anion-specific metallogel.

Neutral Organometallic Halogen Bond Acceptors: Halogen Bonding in Complexes of PCPPdX (X = Cl, Br, I) with Iodine (I(2)), 1,4-Diiodotetrafluorobenzene (F4DIBz), and 1,4-Diiodooctafluorobutane (F8DIBu).

The behavior of a sterically crowded neutral pincer {2,6-bis[(di-t-butylphosphino)methyl]-phenyl}palladium (PCPPd) halides, PCPPdX (X = Cl, Br or I), as XB acceptors with strong halogen bond (XB) donors, iodine (I(2)), 1,4-diiodotetrafluorobenzene (F4DIBz), and 1,4-diiodooctafluorobutane (F8DIBu) were studied in the solid state. The co-crystallization experiments afforded high-quality single crystals of XB complexes PCPPdCl-I(2) (1a), PCPPdBr-I(2) (2a), PCPPdI-I(2)(3a), PCPPdCl-F4DIBz (1b), PCPPdBr-F4DIBz (2b), and PCPPdBr-F8DIBu (2c). The 1:1 iodine complexes (1a, 2a, and 3a) all showed a strong halogen bonding interaction, the reduction of the sum of the van der Waals radii of halogen to iodine being 24.6 (1a), 23.9 (2a), and 19.4% (3a) with X···I-I angles of 177, 176, and 179°, respectively. While the pincer palladium chloride 1 and bromide 2 were crystallographically isomorphous and showed similar XB behavior, the palladium iodide complex, 3, exhibited markedly different properties, and unlike 1 and 2 it does not, under similar conditions, result in XB complexes with the weaker XB donors F4DIBz and F8DIBu. The results indicate that PCPPdI is not nucleophilic enough to have XB interactions with other donors than iodine. However, the weaker XB donors F4DIBz and F8DIBu form XB complexes with the chloride 1 and especially with the bromide 2. The prevalence of the halogen bonding with 2 is probably not only electronic in origin, and it seems to offer the best balance between electron poorness and steric availability. The XB interactions with F4DIBz and F8DIBu are much weaker than with iodine, the reduction of the sum of the van der Waals radii of halogen to iodine being 13.5, 12.3, and 14.6% with C-I···X angles between 163 and 179° for 1b, 2b, and 2c, respectively, and results in polymeric (···1···F4DIBz···1···F4DIBz···)(n), (···2···F4DIBz···2···F4DIBz···)(n), and (···2···F8DIBu···2···F8DIBu···)(n) one-dimensional zigzag chains in the solid state.

Fluoride-responsive organogelator based on oxalamide-derived anthraquinone.

Anthraquinone derived oxalamide gelator 1 forms with aromatic solvents and alcohols very stable gels which selectively respond to the presence of fluoride anion by colour change and/or gel-to-sol transition.

Synthesis, structural studies, and biological evaluation of some purine substituted 1-aminocyclopropane-1-carboxylic acids and 1-amino-1-hydroxymethylcyclopropanes.

The novel purine derivatives of 1-aminocyclopropane-1-carboxylic acid (8 and 9) and 1-amino-1-hydroxymethylcyclopropane (12 and 13) with methylene spacer between the base and the cyclopropane ring were prepared by multistep synthetic route involving alkylation of adenine and 6-(N-pyrrolyl)purine with 2-hydroxy-methyl-1-aminocyclopropane-1-carboxylic acid derivative 3 as a key reaction. All novel compounds were racemic. The N-9 substitution of the purine ring and the Z-configuration of the cyclopropane ring in 4-13 were deduced from their 1H and 13C NMR spectra by analyses of chemical shifts, H-H coupling constants and connectivities in two-dimensional homo- and heteronuclear correlation spectra. An unequivocal proof of the stereostructure of 1, 4 and 5 was obtained by their X-ray structure analysis. The novel compounds were evaluated on cytostatic and antiviral activities in several cell lines. The 6-(N-pyrrolyl)purine derivative of 1,2-aminocyclopropane alcohol 12 exhibited a more pronounced inhibitory activity against the proliferation of cervical carcinoma (HeLa) and human fibroblast (WI-38) cells than other types of tumor cell lines. None of the compounds showed inhibitory activities against cytomegalovirus, varicella-zoster virus or other viruses.

Hydrogen bonding in N,N'-bis[(1S)-2-azido-1-(2-methylpropyl)ethyl]oxalamide: twofold symmetry of R(2)(2)(10) hydrogen-bonded dimers connected into an alpha-network.

The title compound, C(14)H(26)N(8)O(2), belongs to a class of retropeptides with an oxalamide unit (-NH-CO-CO-NH-), and is a precursor for the synthesis of an amine-terminal gelator. The compound is a good synthon for one-dimensional hydrogen bonding. The crystal structure reveals a hydrogen-bonded cyclic dimer with unusual twofold rotation symmetry.