Synthesis and structure of 2,6,14- and 2,7,14-trisubstituted triptycene derivatives

A series of 2,6,14- and 2,7,14-trisubstituted triptycene derivatives were efficiently synthesized and their structures were determined by NMR, MS spectra, and X-ray analysis. These trisubstituted triptycenes are potential building blocks for constructing novel receptors and synthetic molecular machines.     

Nitrosonium complexes of triptycene

According to the ¹H and ¹³C NMR data, triptycene reacts with nitrosonium tetrachloroaluminate to form positively charged π-complexes with one and two nitrosonium ions, which are rapidly (on the NMR time scale) converted into each other. DFT quantum-chemical calculations with Λ02 basis set indicated higher stability of singly charged complexes relative to doubly charged. Addition of three nitrosonium ions to triptycene molecule is unfavorable from the energy viewpoint.     

Triptycene quinones in synthesis: preparation of triptycene cyclopentenedione and its reactivity as a dienophile

Triptycenene quinone 1 was converted to triptycene cyclopentenedione 5 through hydroxyquinone-phenyliodonium ylide formation and thermal ring contraction of the latter. Cyclopentenedione 5 reacts as a dienophile and as a dipolarophile with dienes and nitrile oxides, affording polycyclic adducts bearing the triptycene moiety.     

Triptycene: no homoconjugation effect for extending optical properties of π-conjugated oligomers

1,5- and 1,8-bis(bifluorenyl)anthracene were synthesized and converted to their corresponding bis(bifluorenyl)triptycenes and bis(bifluorenyl)-9,10-dihydroanthracenes. Analysis of their optical properties shows no feature of extended conjugation in the triptycene pair. The electronic spectra of the triptycene and dihydroanthracene pairs are in fact superimposable. There is definite evidence that triptycene displays zero homoconjugation effect.     

1D Chain and 3D framework of silver(I) organo-metallic polymers self-assembled with triptycene

For the purpose of investigating the coordination behavior of sterically congested alkenes and exploring the possibility of non-planar complexation in the polycyclic aromatic system for formation of extended polymeric networks, triptycene (tpty) has been studied with regard to its complexation with the silver(I) ion. The crystal structures of [Ag(tpty)(THF)₂](ClO₄) (1) and [Ag₆(tpty)₄(CF₃SO₃)₂(H₂O)₆](CF₃SO₃)₄ (2) have been determined by single-crystal X-ray diffraction. The polycyclic aromatic hydrocarbon triptycene is found to offer a potential site for complexation, which can be utilized to generate an interesting array of organo-metallic polymers with one-dimensional (1D) chain and three-dimensional (3D) porous frameworks.     

Spontaneous formation of triptycene supramolecules on surfaces

In the limit of weak molecular interaction with an inorganic surface, noncovalent interactions between molecules dominate the nucleation and thin-film growth. Here, we report on the formation of three-dimensional triptycene clusters with a particularly stable structure. Once formed at the early stage of molecular adsorption, the clusters are stable for all temperatures until desorption. Furthermore, the clusters diffuse and nucleate as individual entities, therefore constituting building blocks for the later thin-film formation. High resolution scanning tunneling microscopy images indicate that the cluster is stabilized by C-H-pi interactions. The formation of such molecular structures at a surface is possible because the three-dimensional structure of the triptycene molecule leads to a very weak and mobile adsorption state. These results show that it is possible to investigate complex pathways in the formation of three-dimensional supramolecules at surfaces using a scanning tunneling microscope.     

Highly selective synthesis of triptycene o-quinone derivatives and their optical and electrochemical properties

A convenient and efficient method for the selective synthesis of a series of triptycene o-quinone derivatives is described. The triptycene o-quinones, especially the ones containing the methoxy group(s) (electron donor) and the o-quinone group(s) (electron acceptor) simultaneously, show interesting intramolecular CT interactions and electrochemical properties. Moreover, DFT calculations display that introducing a strong electron-donor group into triptycene o-quinone results in an increasing of the HOMO energy level, which subsequently decreases the HOMO-LUMO energy gap.     

Anthracene capped isobenzofuran: a synthon for the preparations of iptycenes and iptycene quinones

Anthracene capped isobenzofuran 5 (5,6-(9,10-dihydroanthracen-9,10-yl)isobenzofuran) was synthesized for the first time. It is a highly reactive and versatile synthon for the synthesis of iptycene derivatives via Diels-Alder reactions. Cycloadducts 10 could be readily deoxygenated to iptycenes 11. Two new reactions of PhI(OAc)(2)/TfOH have been explored. Endoxides 10 were directly oxidized to iptycene quinones 12, and isobenzofuran 5 was conveniently converted to triptycene dialdehyde 16. H-shaped centrally extended pentiptycene quinones 13 and 14 were also synthesized.     

Surface modification of ZIF-90 with triptycene for enhanced interfacial interaction in mixed-matrix membranes for gas separation

Zeolite imidazole framework (ZIF-90) nanoparticles were chemically modified by grafting triptycene moieties. The modified nanoparticles were introduced into a triptycene-based polyimide as fillers to generate mixed matrix membranes (MMMs) for gas separation. The incorporation of “hook-like” triptycene moieties in both dispersed and continuous phases led to intimate contact between the two phases and thus defect-free interfacial morphology, due to the supramolecular interlocking and π–π stacking interaction between triptycene units presented in both phases. The filler/polymer solution showed shear thickening behavior due to such strong interfacial interaction. The separation performance of the prepared composite membranes was investigated as a function of filler loading and particle surface grafting density. Pure-gas permeation results showed that the gas permeabilities increased expectedly as the filler loading increased, with stable or improved selectivities. The reduced permeability relative to pristine polyimide film is likely due to the pore blockage of ZIF-90 upon grafting triptycene moieties on the particle surface. Reducing the grafting density of triptycene moieties led to improved permeability and selectivity suggesting good tunability of this series of new composite membranes. Overall, modification of nanofiller with hierarchical triptycene moieties offers a fundamentally new avenue for creation of composite membranes with unique properties in gas separations.     

Tetrathiafulvalene-functionalized triptycenes: synthetic protocols and elucidation of intramolecular Coulomb repulsions in the oxidized species

A large selection of triptycenes functionalized with tetrathiafulvalene (TTF) units as well as triptycenes containing extended TTFs as a part of the triptycene core have been synthesized utilizing new triptycene di- and tetraaldehydes as well as bis-, tetrakis- and hexakis(bromomethyl) derivatives. The largest scaffold contains a total of 12 TTFs around the central triptycene core. From spectroelectrochemical and chemical oxidation studies, we have elucidated the extent to which an increasing number of electrostatic interactions among oxidized TTF units exert an influence on the absorption characteristics.     

Iptycene quinones: synthesis and structure

A practical and efficient method to synthesize iptycene quinones has been developed. As a result, a series of pentiptycene quinones 8-16 were conveniently synthesized by one-pot reaction of triptycene quinone 4 or 5 with anthracene 1 or its derivatives 2-3 in refluxing acetic acid in the presence of p-chloranil, followed by CAN oxidative demethylation. Similarly, a series of heptiptycene quinones 17-23 with U-shaped cavities were achieved with pentiptycene quinone 10 and triptycene diquinone 6 as precursors. Non-iptycene triquinones 24 with one tweezer-shaped cavity and 25 with two U-shaped cavities were synthesized by one-pot reactions of anthracene with pentiptycene triquinones 16a and 16b, respectively. Non-iptycene triquinone 26 with a dendritic structure was conveniently obtained by the reaction of anthracene with either pentiptycene diquinone 12 or triptycene triquinone 7. The structures of regioisomers 16a and 16b were determined by the single-crystal structure analysis of 16b. The structures of other regioisomers, including heptiptycene tetraquinones 19a/19b/19c and heptiptycene triquinones 23a/23b, were identified by comparative reactions.     

Molecular spur gears comprising triptycene rotators and bibenzimidazole-based stators

Dynamic gearing of molecular spur gears, the most common type of mechanical gear, is elucidated. Molecular design and conformational analysis show that derivatives of 4,4-bis(triptycen-9-ylethynyl)bibenzimidazole represent suitable constructs to investigate gearing behavior of collateral triptycene (Tp) groups. To test this design, DFT calculations (B97-D/Def2-TZVP) were employed and the results suggest that these molecules undergo geared rotation preferentially to gear slippage. Synthesis of derivatives was carried out, providing a series of molecular spur gears, including the first desymmetrized spur gear molecules, which were subsequently subjected to stereochemical analysis.     

Optically transparent,organosoluble poly(ether-amide)s bearing triptycene unit; synthesis and characterization

Abstract

Aromatic polyamides are famous high performance polymeric materials for their excellent thermal, mechanical, electrical properties, which now a days became a dominant platform for modern polymer chemistry area. Triptycene unit like structures in polymer directly affects the physiochemical properties of polymer, thus polyamides especially with triptycene unit in their backbone with aryl ether linkage imparts combination of properties such as better solubility, melts processing characteristics, and better thermal stability in contrast with those of polymers without an aryl-ether linkageNew triptycene-containing bis(ether amine), 1,4-bis(4-aminophenoxy), 2, 3-benzotriptycene (4a) was synthesized from nucleophilic displacement reactions of P-fluoronitrobenzene with 1,4-dihydroxytriptycene, followed by reduction, and elucidated by FTIR, ^1?H, ^13?C NMR spectroscopy and HRMS. A series of new polyamides containing pendant triptycene group and flexibilizing ether linkages was synthesized by polycondensation of diamine with commercially available aromatic diacischlorides viz., terephthalylchloride (TPC), isophthalylchloride (IPC) and varying molar mixture of TPC and IPC accordingly. Synthesized Poly(ether-amide)s were found soluble in common organic solvents such as chloroform, dichloromethane, tetrahydrofuran, DMF, DMAc, DMSO also could be cast into excellent transperent thin films. Inherent viscosities of polyamides were in the range 0.44–0.57 dL/g. Polyamides exhibited initial decomposition temperature (T_i), glass transition temperatures (T_g) and temperature at 10% wt loss (t₁₀), which was determined by TGA were noted in the range 212?°C–305?°C, 295?°C –309?°C and 587?°C–631?°C respectively with 24%–54% char yeild at 900?°C under nitrogen atmosphere, indicating its better thermal stability and moderate glass transition temperature.     

Solid-state molecular folding and supramolecular structures of triptycene-derived secondary dicarboxamides

The synthesis and X-ray crystal structures of triptycene-derived secondary dicarboxamides 1 and 4-7 and reference compounds 2, 3, and 8 are reported. For comparison, molecular conformations of 1-8 in the gas phase and those of 1 and 3-6 in CD2Cl2 investigated by AM1 modeling and 1H NMR spectroscopy, respectively, are also included. The solid-state conformations of 1 and 5-8 are folded and compact, resulting from the cooperative effects of intramolecular amide-amide hydrogen bonding and edge-to-face arene-arene interactions between the triptycene and the N-acetylsulfanilyl groups. The sulfonyl ester groups are also essential in the folding of 1 and 5-8 and function as structural turn units. In contrast, the conformations of 2-4 are unfolded due to the lack of one of these three essentials. The extended triptycene ring systems in 6 and 7 provide an arene-arene contact mode that is different from that for 1 and 5. While AM1 calculations suggest that the two possible arene-arene contact modes in 6 and 7 have similar conformational energies, the one observed in the solid state is also favored in solutions. To achieve a more regular shape for compact crystal packing, the bulky triptycene groups tend to pack in pairs. As a result, the intermolecular amide-amide hydrogen bonding is perturbed and modified with the participation of either the sulfonyl groups or the methanol solvent molecules, leading to various hydrogen-bonding motifs for these triptycene diamides.     

Synthesis and properties of novel triptycene‐based polyimides

Two new triptycene‐containing bis(ether amine)s, 1,4‐bis(4‐aminophenoxy)triptycene ( 4 ) and 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)triptycene ( 6 ), were synthesized, respectively, from the nucleophilic chloro‐displacement reactions of p‐chloronitrobenzene and 2‐chloro‐5‐nitrobenzotrifluoride with 1,4‐dihydroxytriptycene in the presence of potassium carbonate, followed by palladium‐catalyzed hydrazine reduction of the dinitro intermediates. The bis(ether amine)s were polymerized with six commercially available aromatic tetracarboxylic dianhydrides to obtain two series of novel triptycene‐based polyimides 8a – f and 9a – f by using a conventional two‐step synthetic method via thermal and chemical imidizations. All the resulting polyimides exhibited high enough molecular weights to permit the casting of flexible and strong films with good mechanical properties. Incorporation of trifluoromethyl groups in the polyimide backbones improves their solubility and decreases their dielectric constants. The fluorinated polyimides 9d and 9f derived from diamine 6 with 4,4′‐oxydiphthalic anhydride and 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), respectively, could afford almost colorless thin films. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of polycyclic aromatic hydrocarbon-based nanovehicles equipped with triptycene wheels

Two new nanovehicles that have extended aromatic platforms as the cargo zones have been obtained. Two strategies were considered for the formation of the perylene core from two naphthalene precursors. The first was based on a Scholl-type reaction involving an oxidant, and the second used a brominated derivative to perform a homocoupling reaction. The first strategy failed under diverse coupling conditions in the presence of several strong oxidants. Nevertheless, the use of CoF(3) in trifluoroacetic acid triggered a dimerization reaction between two ester groups of one molecule and the naphthalene unit of another, thereby surprisingly yielding a ten-membered carbon macrocycle. The second strategy encountered a lack of reactivity of the substrate under several homocoupling conditions. The dimerization was not easily performed but Ullmann-type conditions ultimately gave the expected product. The low yield and low solubility of the product encouraged us to modify our initial design. The synthesis of a new chassis that incorporated additional tert-butyl groups improved the solubility of the molecules and also prevented overcyclization of the aromatic platform by blocking these positions. Some p-phenylene spacers were also intercalated between the iodine and perylene centers to increase the reactivity of the halide towards coupling reactions. Two new chassis were obtained by Scholl-type oxidative coupling using FeCl(3) as the oxidant. The introduction of four triptycene wheels allowed the formation of the two corresponding nanovehicles.     

Photoresponsive polymers with dangling triptycene units as efficient receptor for fullerene-C60

We report herein a new triptycene derivative ( 1 ) with an azo functional group. This molecule has been used as a monomer to yield two linear polymers ( TAFPs ) that have several triptycene units dangling from the linear polymer chain. TAFPs are soluble in organic solvents and are thermally stable. TAFPs can be cast into thin films. Further, these polymers are fluorescent with emission intensity increasing upon irradiation with ultraviolet light due to photoisomerization of the azo groups present in them. The fluorescence of TAFPs are quenched in the presence of C₆₀, which supports their strong affinity for each other. Since both TAFP1 and TAFP2 form stable thin films of uniform thickness over large area coupled with their interaction with C₆₀, these polymers may find potential applications in the development of optoelectronic devices or as molecular sensors in supramolecular chemistry.     

Photochemical deuterium effect on the rearrangement of triptycene

Triptycene monodeuterated at the bridgehead position shows in direct and sensitized irradiation a photochemical isotope effect k_H/k_D=2.2–2.4. From quantum yield of undeuterated, φ_H,H=0.33 and monodeuterated triptycene, φ_H,D=0.24 was concluded that the effect stems from differences in the reaction rates and not from differences in the radiationless deactivations.     

Epitaxygens: mesomorphic properties of triptycene derivatives

The structure of mesophases derived from a triptycene subunit substituted with five paraffinic chains has been determined by X-ray diffraction at small angles. They all show a smectic ordering. This is the first example of a smectogen whose rigid core belongs to the D_3h symmetry. A hexagonal order has been observed in the X-ray diffraction patterns; it has been associated with a p31m packing of the rigid cores within the layers. The intralamellar cell parameter is in agreement with the molecular dimensions determined from CPK models. The calculated molecular length is in accordance with the experimental interlamellar distance. The difference in mesomorphic behaviour between the five and six chain derivatives is discussed.     

Synthesis of bridgehead-functionalized triptycene quinones via Lewis acid–promoted Diels-Alder reaction of 9-acyloxyanthracenes

Herein, we show that bridgehead-functionalized triptycene quinones can be rapidly and conveniently prepared in good to high yields by Lewis acid–catalyzed cycloaddition of 1,4-benzoquinones and 1,4-naphthoquinones to 9-acyloxyanthracenes and probe the substrate scope of this transformation.