Αggregation of phenylacetylene macrocycles (PAMs) in solution has been studied by 1H NMR spectroscopy and vapor pressure osmometry. The association constant for dimerization, K assoc, has been determined by curve fitting the concentration dependence of 1H NMR chemical shifts to a model for monomer−dimer equilibrium. The reliability of the NMR-determined aggregation constants and aggregate size have been independently verified by vapor pressure osmometry measurements. Thermodynamic parameters for association have been obtained from van't Hoff analyses which show the aggregation to be favored enthalpically. The aggregation of PAMs bearing various endo- and exo-annular functional groups and PAMs of different geometry and ring size has been studied. The type of pendant functional groups and the manner in which these groups are arranged on the macrocycle is shown to strongly influence self-association. PAMs substituted with electron withdrawing groups (e.g., esters) are more strongly associated than those bearing electron donating groups (e.g., alkyl ethers) or macrocycles bearing a combination of the two substituents. The type of alkyl substituent on the ester or ether group is less important as long as the substituent is not branched and is exo-annular. Endo-annular alkyl ethers as well as branched exo-annular alkyl esters severely disrupt aggregation. Rigidity of the macrocycle also influences self-association. In contrast to hexameric macrocycles, similarly substituted open-chain oligomers and a nonplanar macrocycle show much weaker association. These findings are discussed in the context of face-to-face π−π interactions between aromatic rings. Consideration has also been given to π−π interactions between aromatic and ethynyl groups and between a pair of acetylenes, but these are concluded to be less significant based on an analysis of data from the Cambridge Structural Database.

The synthesis of a new conjugated rigid-rod polyquinoline, poly(2,29-(p-phenylene)-6,69-bis(4-(p-tert-butylphenyl)quinoline)), and its incorporation in light-emitting diodes as the emissive layer are reported. These electroluminescent devices, containing 1,1-bis(di-4-tolylaminophenyl)cyclohexane (TAPC) dispersed in polystyrene as the hole-transport layer, emit bright yellow light (k max = 554 nm) with a quantum efficiency of 0.26% photons/electron and a luminance of 280 cd/m 2 at a current density of 100 mA/cm 2 . These results also demonstrate that the new polyquinoline is a good n-type (electron transport) electroluminescent material.Conjugated rigid-rod polyquinolines have excellent thermal stability and high mechanical strength [1, 2]. These n-type semiconducting polymers [3] have interesting electronic [2 b], photoconductive [4], and nonlinear optical [5] properties. Recently, some polyquinolines were used as both the electron-transport layer and an emission layer in polyquinoline/poly(p-phenylenevinylene) heterojunction light-emitting diodes (LEDs) [6]. The attractive combination of excellent thermal, mechanical, and optoelectronic properties of the conjugated polyquinolines has motivated our synthesis of new derivatives for electroluminescent device applications.The conjugated rigid-rod polyquinolines have limited solubility in common organic solvents. They are, however, highly soluble in common organic solvents as Lewis acid (GaCl 3 , AlCl 3 ) or alkyl/aryl phosphate complexes [1 a, 2a]. To simplify thin film processing and improve optoelectronic properties of the polyquinolines for device applications, we are currently exploring the synthesis of conjugated polyquinoline derivatives that may have an inherent solubility in organic solvents through side group substitution, which could also influence the electronic structure and optical properties. A previous attempt at improving the solubility of rigid-rod polyquinolines by appending aryl ether groups to the polymer backbone via a fairly involved synthesis of the monomers was unsuccessful [7]. In this paper, we report the synthesis, photoluminescence, and electroluminescence of a new conjugated polyquinoline, poly(2,29-(p-phenylene)-6,69-bis(4-(p-tertbutylphenyl)quinoline)) (Bu-PPQ, 2). The related poly(2,29-(p-phenyl)-6,69-bis (4-phenylquinoline)) (PPPQ, 1) is known to be soluble in protonic acid solvents (methanesulfonic acid, trifluoroacetic acid, and formic acid), dim-cresyl phosphate/m-cresol, and Lewis acid/nitromethane solutions from which thin films can be prepared [2]. In Bu-PPQ (2), two tert-butyl groups were incorporated into the pendant phenyl groups of the polymer as shown in Scheme 1.The new monomer 3,39-di(499-tert-butylbenzoyl)benzidine (10) was synthesized according to a modified literature procedure (Scheme 1) [1 b]. Treatment of bromide 3 with potassium cyanide in acetonitrile at room temperature afforded nitrile 4 [8] in quantitative yield, which on condensation with 5 in basic methanol yielded anthranil 6 [9]. Reduction of the anthranil...

No abstract

The assembly of amphiphilic phenylacetylene macrocycles (PAMs), with molecular structures that vary in terms of the nature and orientation of their pendant functional groups, has been studied on a Langmuir−Blodgett trough and after transfer onto solid substrates. These monolayer films are of interest as two-dimensional host matrices and shape selective membranes whose two-dimensional organization should bring together shape selective compartments. The disk-like PAMs can, in principle, adopt orientations in which the plane of the macrocycle can range from perpendicular (edge-on) to parallel (face-on) at the interface. PAMs functionalized with six hydrophilic groups around the periphery do not prefer the face-on orientation and are most likely tilted, perhaps in a poorly organized state. PAMs that have spatially segregated hydrophilic and hydrophobic groups adopt the edge-on orientation when the hydrophilic moieties are carboxylate groups. In contrast, PAMs appended with acid moieties do not lead to stable monolayers, most likely because they engage in strong intermolecular hydrogen bonding interactions as evidenced by 1H NMR and vapor pressure osmometry of the solutions. Monolayers of the dicarboxylate PAMs were transferred onto fused silica and Si(100) surfaces and these were in turn characterized by contact angle, ellipsometry, absorption FTIR, and angle-resolved X-ray photoelectron spectroscopies. Taken together these characterization experiments strongly support the hypothesis that the dicarboxylate PAMs form a well-ordered and stable two-dimensional array and that they adopt the edge-on configuration with near-vertical orientation of the macrocycle plane.

No abstract