Arene Units Research Articles

"Head-to-head" double-hamburger-like structure of di-ruthenated d(GpG) adducts of mono-functional Ru-arene anticancer complexes.

Guanine bases in DNA are targets for some Ru-arene anticancer complexes. We have investigated the structure of the novel di-ruthenated d(GpG) adduct Ru2-GpG (where Ru = {(η6-biphenyl)-Ru(en)}2+ (1')) in aqueous solution. 2D NMR results indicate that there are two conformers, supported by modeling studies. The major conformer I is a novel double-hamburger-like structure with a "head-to-head" (HH) base arrangement involving hydrophobic interactions between neighboring arene rings, the first example of a HH d(GpG) adduct constructed by weak interactions. Hence there are significant differences compared to Pt-d(GpG) adducts formed by cisplatin. There is no obviously rigid bending for the major conformer I. The minor conformer II of Ru2-GpG has a back-to-back structure, with two ruthenated guanine bases flipped away from each other. 19-23 base-pair oligodeoxyribonucleotides containing central TGGT sequences di-ruthenated by 1 show no directional bending, only slightly distorted di-ruthenated duplexes, consistent with the NMR data for conformer I. The structural differences and similarities of d(GpG) residues which are di-ruthenated or cross-linked by platination are discussed in the context of the biological activity of these metal complexes.

Efficient epoxide isomerization within a self-assembled hexameric organic capsule

The supramolecular organic nano-capsule formed by the self-assembly of six resorcin[4]arene units efficiently promotes the isomerization of epoxides (Meinwald isomerization) to the corresponding carbonyl compounds.

Versatile Architectures of Silver(I) Organometallic Polymers with Tetra-allyl Functionalized Calix[4]arene Fine-tuned by Distinct Anions

Two silver(I)-organometallic polymers have been constructed by utilizing the different silver(I) salts and a bowl-shaped calix[4]arene functionalized with tetra-allyl groups on the upper rim (L). Reacted with AgClO4 to afford 1, 1 exhibits a two-dimensional (2D) structure, where tetra-allyl-functionalized calix[4]arene units are linked through Ag–alkene interaction to generate wave-like organometallic chains and further connected by bridging by acetone molecules to afford a 2D network, giving a 2,4,4-net with the point (Schlafli) symbol {42·82·102}{42·84}2{4}2. Substituting ClO4– by NO3– as the counteranion of silver(I) salt, a three-dimensional organometallic polymer (2) encapsulating solvent molecules in the cavities was generated by connection of 2D inorganic AgNO3 layers and pillared L ligands, which gave a 3,3,4,4-net with the point (Schlafli) symbol {6·7·8}2{62·7·82·9}2{62·72·92}{62·7}2. In addition, thermogravimetric analysis, luminescent properties, and voltammetric behavior of 1 and 2 also have b...

The synthesis and structures of arene-substituted azadipyrromethenes

We present the synthesis of several azadipyrromethenes with four peripheral arene units which can be readily generated via the well-established chalcone synthetic method. The stability and yields of these azadipyrromethenes is highly dependent on the nature of the arene substituent, with the bis-pyridine systems exhibiting the highest degree of instability. The structures of several of the compounds and their BF2 adducts are presented; intramolecular hydrogen bonding is observed in the free base ADPMs. We also present a study into the absorption and emission properties of the ADPMs and their BF2 adducts and observe that they are also highly dependent on the identity of the substituents.

Calix[4]arene-Functionalised Silver Nanoparticles as Hosts for Pyridinium-Loaded Gold Nanoparticles as Guests.

A series of lipophilic gold nanoparticles (AuNPs) circa 5 nm in diameter and having a mixed organic layer consisting of 1-dodecanethiol and 1-(11-mercaptoundecyl) pyridinium bromide was synthesised by reacting tetraoctylammonium bromide stabilised AuNPs in toluene with different mixtures of the two thiolate ligands. A bidentate ω-alkylthiolate calix[4]arene derivative was instead used as a functional protecting layer on AgNPs of approximately 3 nm. The functionalised nanoparticles were characterised by transmission electron microscopy (TEM), and by UV/Vis and X-ray photoelectron spectroscopy (XPS). Recognition of the pyridinium moieties loaded on the AuNPs by the calix[4]arene units immobilised on the AgNPs was demonstrated in solution of weakly polar solvents by UV/Vis titrations and DLS measurements. The extent of Au-AgNPs aggregation, shown through the low-energy shift of their surface plasmon bands (SPB), was strongly dependent on the loading of the pyridinium moieties present in the organic layer of the AuNPs. Extensive aggregation between dodecanethiol-capped AuNPs and the Ag calix[4]arene-functionalised NPs was also promoted by the action of a simple N-octyl pyridinium difunctional supramolecular linker. This linker can interdigitate through its long fatty tail in the organic layer of the dodecanethiol-capped AuNPs, and simultaneously interact through its pyridinium moiety with the calix[4]arene units at the surface of the modified AgNPs.

Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene-Crown Ether Fused Tricyclic Host.

A novel tricylic host molecule 1 that consists of two pillar[5]arene units and a crown ether ring was found to selectively bind two kinds of guest molecules with different shapes, sizes, and electronic constitutions, namely 1,4-dicyanobutane G1 and paraquat G2, with its two macrocyclic subunits, to form a four-component complex 2G1⊂1⊃G2. An (1)H NMR study of stepwise bindings of G1 and G2 to host 1 in CDCl3/DMSO-d6 revealed that the strength of the association between complex 2G1⊂1 and guest G2 was only one-fourth of that between free 1 and G2, demonstrating a negative heterotropic cooperativity of G1 in the binding of G2 to host 1.

A new perylene bisimide-armed calix[4]-aza-crown as “turn on” fluorescent sensor for Hg2+ ion and its application to living cells

We report the design and synthesis of a new perylene bisimide derivative containing calix[4]arene units (PB-CX[4]) as “turn on” fluorescent sensor for Hg2+ ion determination. PB-CX[4] showed highly selective and sensitive “turn-on” fluorescent responses toward Hg2+ ion based on photoinduced electron transfer (PET) mechanism in DMF/H2O (v/v, 95/5). The binding analysis using a Job plot suggested that PB-CX[4] formed a 1:2 complex with Hg2+. The association constant (K) of PB-CX[4]–Hg2+ complex was found to be 1.66×109M−2, with a detection limit of 5.56×10−7M. In addition, possible utilization of PB-CX[4] as bio-imaging fluorescent probe to detect Hg2+ in human colon cancer cell lines was also observed by confocal fluorescence microscopy.

ChemInform Abstract: Synthesis of Substituted Iptycenes

AbstractReview: [47 refs.

New 5,17-(di-ionizable)-25,26,27,28-tetraalkoxycalix[4]arene ligands: synthesis and selected divalent metal ion extractions

Four new series of 5,17-(di-ionizable)-25,26,26,28-tetraalkoxycalix[4]arene ligands are prepared. The ionizable groups are carboxylic acid and N-(Z)sulfonyl formamide functions with Z = –Me, –Ph, –C6H4–4-NO2, and –CF3. When the four alkoxy groups are methoxy, the ligand conformation is flexible. With four butoxy groups, the ligands are locked in cone, partial-cone, or 1,3-alternate conformations. Complexation abilities of the new ligands are evaluated in solvent extractions of selected divalent metal ions from aqueous solutions into chloroform. Both the conformation of the calix[4]arene unit and identity of the acidic group are found to influence the divalent metal ion extraction selectivity and efficiency.

Ion pair-induced conformational motion in calix[4]arene-strapped calix[4]pyrroles.

In order to understand the still-poorly understood interplay between calix[4]arene conformations and cation and anion recognition in multicomponent systems, the ion pair receptors 1 and 2 were synthesized. In solution and in the solid state, the calix[4]arene subunit of receptor 1 adopts a cone conformation, while that of 2 interconverts between the cone and the partial cone conformation. These geometric features differ from previous systems where the calix[4]arene moiety was locked in the 1,3-alternate conformation. A combination of 1H NMR spectroscopic analyses and single crystal X-ray diffraction studies reveal that receptor 1 binds the fluoride and the chloride anion via significantly different binding modes, displaying, for instance, 1 : 1 and 2 : 3 binding stoichiometries with CsF and CsCl, respectively. In the case of 2, the conformation of the calix[4]arene constituent of 2 is highly dependent on the size and quantity of anions present. For example, upon treatment of 2 with the fluoride anion (as both the TBA+ and Cs+ salts), the calix[4]arene unit coexists as cone and partial cone conformers that are inter-convertible. In the presence of excess CsF, the aromatic rings of the calix[4]arene subunit becomes locked in the pinched cone conformation with the result that an ion pair-mediated coordination polymer is formed. In the presence of excess CsCl, the calix[4]arene unit of 2 adopts only the partial cone conformation stabilized by aryl CH-anion hydrogen bonding interactions. The present systems constitute a rare set of related receptors wherein the effects of conformational changes are so tightly coupled with ion recognition.

Substrate selective amide coupling driven by encapsulation of a coupling agent within a self-assembled hexameric capsule.

Encapsulation of a cationic carbodiimide condensing agent within a self-assembled hexameric capsule made of resorcin[4]arene units provides a nano-environment that efficiently steers the substrate selectivity in the amide synthesis reaction between carboxylic acids and primary amines. While in solution pairs of acids react similarly with a given amine, in the presence of the capsule the formation of the shorter amide is greatly favored.

Synthesis of Substituted Iptycenes

Iptycenes are a class of aromatic compounds that contain several arene units fused to a bicyclo[2.2.2]octatriene bridgehead system. This unique, rigid, three-dimensional molecular structure provides several open electron-rich cavities with an abundance of reactive positions, and makes them useful for a wide range of applications. There is no doubt that the synthesis and reactions of iptycene derivatives with different functional groups form the fundamental basis of iptycene development. In this account, the synthesis of substituted iptycenes is described. In particular, the different synthetic strategies toward substituted triptycenes and pentiptycenes are the main focus. 1 Introduction 2 Synthesis of Substituted Triptycenes 2.1 Direct Diels–Alder Addition Reactions 2.2 Selective Substitution of the Triptycene Skeleton 2.2.1 Acetylation 2.2.2 Nitration 2.2.3 Halogenation 3 Synthesis of Substituted Pentiptycenes 4 Synthesis of Other Substituted Iptycenes 5 Conclusion and Outlook

Preparation and characterization of new optically active poly(amide-imide)s and poly(ester-imide)s containing calix[4]arene units

This article describes the synthesis and characterization of new optically active polymers containing upper rim calix[4]arene from the polycondensation reaction of 5,11,17,23-tetra-tert-butyl-25,27-bis[(4-aminobenzyloxy)-6,28-dihydroxy] calix[4]arene with N,N′-pyromellitoylimido-bis-L-alanine diacid chloride (6a) and N,N′-pyromellitoylimido-bis-L-phenyl alanine diacid chloride (6b). This optically active diacidchlorides 6a and 6b have been prepared from the reaction of pyromellitic dianhydride with two chiral amino acids, alanine and phenyl alanine. The chiral poly(amide-imide)s and poly(ester-imide)s obtained in good yield and moderate inherent viscosity. All the polymers have been fully characterized by FTIR, 1H NMR spectroscopy and elemental analysis.

A tryptophan responsive fluorescent and wettable dual-signal switch.

A new fluorescent dianthracene calix[4]arene (C4DA) was designed and synthesized via coupling the fluorescent anthracene units and calix[4]arene units. Then it was used to form self-assembled monolayers (C4DA-SAMs) by the simple click reaction to give the first fluorescent and wettable dual-signal switch for tryptophan (Trp) on a micro- and nano-structured silicon surface. The switch for Trp on the C4DA functional surface was confirmed by contact angle (CA) measurements and fluorescent spectroscopy (FL). Furthermore, the wettability-responsive C4DA functional interface can be re-used for six cycles. The responsive switch can potentially be applied in many fields including nanodevices and intelligent microfluidic switching.

Palladium‐Catalyzed Dithiolation of Platinum(II) Alkynylarylacetylides with Diphenyl Disulfide Leading to Construction of π‐Conjugated Systems with Platinum and Thio Groups

Abstractπ‐Conjugated systems consisting of platinum, sulfur, alkyne, and arene units were synthesized by palladium‐catalyzed addition of organic disulfides to platinum acetylides. When diphenyl disulfide was treated with platinum(II) complexes containing extended alkynyl ligands, trans‐(R3P)2Pt(C≡C–Ar–C≡C–H)2, in the presence of Pd(PPh3)4 catalyst, new sulfur‐containing platinum(II) bis(alkenylarylacetylide) complexes were regioselectively synthesized in good yields. The absorption and luminescence spectra indicated that the emission exhibited in the range 411–415 nm depends on the nature of the acetylide ligand bound to platinum.

Host-guest complexes of calix[4]tubes - prediction of ion selectivity by quantum chemical calculations VI

The selectivity of the bis(calix[4]arene)tetraethylene abbreviated as calix[4]tube for the endohedral complexation of alkali and alkaline earth metal ions, was predicted on the basis of structures and complex formation energies computed with three different quantum chemical methods: DFT LANL2DZp)/LANL2DZp), PM3/SPASS, and PM6. A comparison with published X-ray structures demonstrated that the most reliable results were achieved applying DFT calculations. The complexation of K⁺ and Ba²⁺ is most favorable, followed by the encapsulation of Rb⁺ and Sr²⁺, respectively. The flexibility of the tube, described by the torsion angles associated with the ethylene linkages between the calix[4]arene units and phenyl rings intersecting the plane of the four methylene carbon atoms, also makes an important contribution to its selectivity. In general, the cavity size is similar to [2.2.2] and [N2N2N2], the cryptands with the largest cavities previously studied in our group applying a similar protocol.

Novel chiral (salen)Mn(iii) complexes containing a calix[4]arene unit in 1,3-alternate conformation as catalysts for enantioselective epoxidation reactions of (Z)-aryl alkenes

Two new chiral calix[4]arene-salen ligands 1a,b, based on calix[4]arene platforms in 1,3-alternate conformation, have been prepared by a new general synthetic pathway. Their Mn(III) complexes, 3a,b have shown fairly good efficiency in the asymmetric epoxidation of styrene and substituted styrenes, whereas excellent catalytic activity and selectivity were observed with rigid bicyclic alkenes, namely 1,2-dihydro-naphthalene and substituted 2,2'-dimethyl-chromene. The higher catalytic properties of 3a may be ascribed to the more rigid and inherently chiral structure as proved by molecular modelling, NMR spectroscopy and X-ray data of the similarly structured UO2 complexes 2a,b.

Construction of muscle-like metallo-supramolecular polymers from a pillar[5]arene-based [c2]daisy chain

A muscle-like metallo-supramolecular polymer based on a solvent-driven [c2]daisy chain has been prepared from an amino-modified pillar[5]arene. The integration of terpyridine moieties on both ends of the [c2]daisy chain and the stiff architecture of pillar[5]arene units facilitated the efficient formation of the metallo-supramolecular polymer.

Role of the Comonomeric Units in Reaching Linear Backbone, High Solid-State Order and Charge Mobilities in Heptacyclic Arene-Based Alternating Copolymers

Unpredictable trends of charge mobility (μ) in multicyclic heteroarenes-contained polymers remain an obstacle in designing high performance polymers used in polymeric field effect transistors (PFETs). The roles of the comonomeric units in reaching high hole mobility (μh) of copolymers containing a heptacyclic arene unit, dithienocyclopentacarbazole (DTCC) were investigated in this study. A series of four DTCC-based alternating copolymers, PDTCC-1T, PDTCC-3T, PDTCC-BDT, and PDTCC-TT, were synthesized from the Pd-catalyzed copolymerizations between DTCC and comonomeric units including thiophene (1T), terthiophene (3T), benzodithiophene (BDT) and thienothiophene (TT) units. Among the four DTCC-based alternating copolymers, highest mobility of 1.36 × 10–2 cm2 V–1 s–1 was reached in PDTCC-3T. Optoelectronic and 2D-WAXD studies revealed that strong electronic interaction and highly ordered solid-state structure were only observed in PDTCC-3T. It is attributed to the combination of two axisymmertric units, DTCC and 3T, linearized the polymer backbone, leading to a compact solid-state packing and high μh, while centrosymmertic comonomeric units, BDT and TT curved the polymer backbones of PDTCC-BDT and PDTCC-TT, which decreases solid-state order and μh. Furthermore, the short axisymmeritric 1T although results in a linear backbone of PDTCC-1T, comparing to 3T, it is too short to effectively reduce interchain steric hindrance caused by the solubilizing octyl chains on DTCC. Thus, effective π–π stacking is hindered in PDTCC-1T, resulting in low μh. The macroscopic performances of μhs agreed well with the optoelectronic and 2D-WAXD studies. It is concluded that the linear backbone of DTCC copolymers is the prerequisite to reach ordered solid-state packing, which facilitate effective charge transport, and it depends on the prudent choose on the symmetry of the comonomeric unit. In addition, balance between the solubility and adequate crowdedness of lateral side chains is essential for a PFET material to be not only easily processed, but also effectively π–π stack.

ChemInform Abstract: Pillararenes: Versatile Synthetic Receptors for Supramolecular Chemistry

AbstractReview: 50 refs.