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Three bimetallic triangles were constructed via a step-wise assembly of tailored terpyridine building blocks. Oligomeric trimer 2 was obtained by reacting ligand 1 with Ru(II). Subsequent cyclization of trimer 2 with Zn(II), Cd(II), and Fe(II) resulted in the formation of bimetallic triangles 3, 4, and 5 in high yield, respectively. All triangles were characterized by NMR spectroscopy, ESI and travelling-wave ion mobility-mass spectrometry (MS), as well as gradient MS, which provided insight into their stabilities.

Planar, terpyridine-based metal complexes with the Sierpinski triangular motif and alkylated corners undergo a second self-assembly event to give megastructural Sierpinski pyramids; assembly is driven by the facile lipophilic-lipophilic association of the alkyl moieties and complementary perfect fit of the triangular building blocks. Confirmation of the 3D, pyramidal structures was verified and supported by a combination of TEM, AFM, and multiscale simulation techniques.

The quantitative, single step, self-assembly of a shape-persistent, three-dimensional C3v-symmetric, triptycene-based tris-terpyridinyl ligand initially gives a platonic-based cubic architecture, which was unequivocally characterized by 1D and 2D NMR spectroscopy, mass spectrometry, and single crystal X-ray structural analysis. The unique metal-ligand binding properties of the Cd2+ analogue of this construct give rise to a concentration-dependent dynamic equilibrium between cube, prism, and tetrahedron-shaped architectures. Dilution transforms this cube into two identical tetrahedra through a stable prism-shaped intermediate; increasing the concentration reverses the process.

This overview describes our research progression from the study of heterocycle synthesis to dendritic architecture to simple metallomacrocycles, and finally to complex, fractal-based, suprametallomolecular materials. Construction of the first terpyridine-modified dendritic scaffold was followed by the construction and self-assembly of polyterpyridine monomers. Preparation of tristerpyridine building blocks used in concert with bisterpyridine analogs facilitated access to a Sierpinski gasket, as verified by direct visual observation with UHV-STEM, as well as other techniques. Numerous examples of heteroleptic self-assembly are described that include the quantitative preparation of a Sierpinski triangle. Addition of angled spacer moieties within polyterpyridine building blocks has generated a new family of 3D spherical materials that has facilitated the construction of hybrid fractal-dendritic materials that exhibit the unexpected concentration mediated, architectural transformations.

A novel terpyridine-based, trapezoidal architecture was synthesized by a coordination-driven multicomponent assembly and features three different tpy-M2+-tpy bonds (M2+ = Ru2+, Fe2+, and Zn2+) in the macrocyclic ring. This trimetallic macrocycle introduces the construction of polymetallosupramolecular assemblies possessing multiple, differing metal centers in an ordered, predetermined pattern. Characterization was accomplished by NMR spectroscopy, mass spectrometry, and UV-Vis spectroscopy.

The design and construction of a novel terpyridine-based, dimetallic, 2D [4]triangulane architecture are reported. Synthesis of the metallotriangulane is achieved by multicomponent stepwise assembly of six bidentate and three tetradentate monomers. Characterization was accomplished by NMR spectroscopy, mass spectrometry and TEM microscopy.

A novel, tetrakisterpyridinyl-substituted porphyrin underwent self-assembly to form a three-dimensional, belt-shaped metallomacrocycle, which was characterized by 1D and 2D NMR and electrospray ionization traveling wave ion mobility mass spectrometry.

A series of coordination-driven, heteroleptic self-assembled, bowtie-shaped bis-macrocycles were designed and constructed by combining tetrakis(terpyridinyl)thianthrene and bis-terpyridine, 60°-directed, Ru2+ dimers. The resulting complexes were characterized by NMR spectroscopy and ESI-MS coupled with travelling wave ion mobility spectrometry (ESI-TWIM-MS) experiments. The desired bis-macrocycles were obtained in quantitative yields through the use of long alkyl-chain substituents, in contrast to the lower yields obtained for smaller alkyl moieties.

The preparation of multi-metallic Au nanocluster and nanowires has been achieved using terpyridine-based metallo-organic polymers as multi-ionic templates through a straightforward counterion exchange with aqueous NaAuCl4 followed by a mild reduction in-situ with sodium citrate. The mild reduction of the [TpyFeTpy]2+ x 2[AuCl4]- complex, derived from [TpyFeTpy]2+ x 2Cl- 1 (tpy = 2,2':6',2"-terpyridine), led to the formation of Au nanoclusters (Au NC) with diameters ranging from 7.5-88 nm. Each Au NC alone contained multiple nanoparticles, with diameters ranging from 2.5-4.5 nm. 1,4-bis-terpyridine based metallo-oraganic polymer [-TpyFeTpy-TpyFeTpy-]n(2n+) x [Cl]2n- 2 was found to generate a multi-ionic metallo-polymer with AuCl4- as the counterion, after mild reduction with sodium citrate, resulting in irregular zigzag shaped Au nanowires (Au NW). The prepared Au NW from the di-metallic complex 3 should find applications within electronic devices. Both Au NC and NW were also found to possess excellent catalytic properties.

A Ru(2+)-connected, metallo-organic ligand (L) with three free terpyridines was designed and synthesized. L was assembled with Zn(2+) to generate a helical structure; however, when mixing L with a 1,2,3-tristerpyridine ligand (T), a thermodynamically stable 2D rhombus was assembled. Furthermore, this 2D rhomboidal structure can also be achieved through the dynamic transformation of preassembled helix H with T and Zn(2+) at room temperature.

Hierarchical construction of a highly ordered supramolecular array has been, in general, a challenge due to the complexation of building blocks and the hard-to-control weak interactions. Herein, we present a type of well-ordered nanoribbon, which was self-assembled via shape complimentary and hydrophobic effects from the bowl-shaped supramolecular components, which were synthesized by combining designer terpyridine-based monomers and two different metal ions (Ru2+, Zn2+). Interestingly, switching counter ions or changing monomer concentrations, a transformation between a uniform nanosphere and nanoribbon occurred. This opens a door to fabricate readily tailorable, large-scale, supramacromolecular materials.

Used individually or combinatorially, unique isocyanate-based dendritic monomers generate homo- and heterofunctional materials (the sketch shows schematically a molecule with a heterofunctional surface). Tier construction by combinatorial monomer addition offers new avenues to macromolecular architectural design and the control of physical properties.

The one-step synthesis of the first homoleptic metallomacrocycle is reported. Characterization of the OsII complex, along with its FeII and RuII analogues, was accomplished by NMR spectroscopy, ESI-MS, TWIM-MS, gradient tandem-MS, CV, luminescence and UV/Vis spectroscopy. Center-of-mass collision energies, derived from gradient tandem-MS, reveal that the -based structures are more stable than those of .

Inspiration for molecular design and construction can be derived from mathematically based structures. In the quest for new materials, the adaptation of new building blocks can lead to unexpected results. Towards these ends, the quantitative single-step self-assembly of a shape-persistent, Archimedean-based building block, which generates the largest molecular sphere (a cuboctahedron) that has been unequivocally characterized by synchrotron X-ray analysis, is described. The unique properties of this new construct give rise to a dilution-based transformation into two identical spheres (octahedra) each possessing one half of the molecular weight of the parent structure; concentration of this octahedron reconstitutes the original cuboctahedron. These chemical phenomena are reminiscent of biological fission and fusion processes. The large 6 nm cage structure was further analyzed by 1D and 2D NMR spectroscopy, mass spectrometry, and collision cross-section analysis. New routes to molecular encapsulation can be envisioned.

Preparation of a new water-soluble, cellulose derivative via a supramolecular route is presented. In a one-step procedure, carboxymethyl cellulose (CMC) was reacted with the Cu(BF4)2 complex of 4′-chloro[2,2′:6′,2″]terpyridine to generate the desired CMC–CuII–terpyridine derivative. This polymeric salt was characterized by elemental analysis, ultraviolet–visible spectroscopy (UV–visible), Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), rheological properties measurements, thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), and tensile strength properties testing. In addition, antimicrobial properties were demonstrated against Gram-positive bacteria (Staphylococcus aureus and Streptococcus thermophilus), Gram-negative bacteria (Escherichia coli), and yeast (Saccharomyces cervisiae). The minimum inhibitory concentration of the prepared metallo-terpyridine CMC derivative against the studied microorganisms ranged from 6 to 8 mg/L to achieve ≥90% of microbial growth inhibition.

A bismetallo-organic polymer was successfully prepared by treating a metallo-ligand with Ag+; characterization was accomplished by NMR, UV-vis, and single crystal X-ray analyses. This heteronuclear polymer achieved more than a two-fold turnover number (TON) and a faster reaction rate in comparison to a Ce-driven Ru-monomer in catalytic water oxidation.

The iterative synthetic protocols used for dendrimer construction were developed based on the desire to easily craft highly branched macromolecules with ideally an exact mass and tailored functionality. Inspired by arboreal design and precursors of the utilitarian macromolecules known as dendrimers today, our first examples employed predesigned, 1 → 3 or 1 → (1 + 2) C-branched, building blocks. Physical characteristics of the dendrimers, including their globular shapes, excellent solubility, and demonstrated aggregation, revealed the inherent supramolecular potential. The architecture that is characteristic of dendritic materials also exhibits obvious fractal qualities based on self-similar, repetitive, branched frameworks. Thus, both the fractal design and supramolecular aspects of these constructs are suggestive of a larger field of fractal materials that incorporate repeating geometries and are derived by complementary building block recognition and assembly. Use of 〈terpyridine-M(2+)-terpyridine〉 connectivity for the sides and tuned directed organic vertices has opened the door to other types of novel materials. This approach also circumvents the nonideality of dendrimers, since the heteroleptic, one-step, spontaneous self-assembly process facilitates quantitative outcomes.

Synthesis of giant unimolecular dendrimers is challenging due, in part, to difficulties encountered at higher generations, in both convergent and divergent protocols because of the multistep construction/purification process. Herein, we report a hybrid synthetic procedure in which the core is constructed last. This quantitative assembly generated a metallodendrimer that is supercharged (120+), large (11.3 nm diameter), and its core was previously established. The series of complexes has been unequivocally characterized by NMR, ESI-IM-MS, and TEM techniques.

A three-dimensional, highly symmetric sphere-like nanocage was synthesized using a terpyridine (tpy)-based, flexible tris-dentate ligand and characterized by single crystal X-ray analysis. To introduce more rigidity, one of the tpy units of the tris-dentate ligand was preblocked by stable connectivity to form the corresponding Ru2+-dimer. The complexation between Ru2+-dimer and Fe2+ demonstrates an unexpected temperature-dependent assembly between two irreversible isomeric 3D nanocages. Investigation of the coordination process and structural configurations of the metal–ligand framework, affected by the introduction of rigidity and in the presence of external stimuli (temperature), is reported.

A novel terpyridine-based architecture that mimics a first-generation Sierpinski triangle has been synthesized by multicomponent assembly and features tpy-Cd(II)-tpy connectivity (tpy=terpyridine). The key terpyridine ligands were synthesized by the Suzuki cross-coupling reaction. Mixing two different terpyridine-based ligands and Cd(II) in a precise stoichiometric ratio (1:1:3) produced the desired fractal architecture in near-quantitative yield. Characterization was accomplished by NMR spectroscopy, mass spectrometry, and transmission electron microscopy.

A facile high yield, self-assembly process that leads to a terpyridine-based, three-dimensional, bis-rhomboidal-shaped, molecular wheel is reported. The desired coordination-driven supramolecular wheel involves eight structurally distorted tristerpyridine (tpy) ligands possessing a 60° angle between the adjacent tpy units and twelve Zn(2+) ions. The tpy ligand plays dual roles in the self-assembly process: two are staggered at 180° to create the internal hub, while six produce the external rim. The wheel can be readily generated by mixing the tpy ligand and Zn(2+) in a stoichiometric ratio of 2:3; full characterization is provided by ESI-MS, NMR spectroscopy, and TEM imaging.

The design and construction of the first multicomponent stepwise assembly of atpy-Ru(II) -tpy-based (tpy=terpyridine), three-dimensional, propeller-shaped trismacrocycle, 8, are reported. Key steps in the synthesis involve the preparation of a hexaterpyridinyl triptycene and its reaction with dimeric, 60°-directional, bisterpyridine-Ru(II) building blocks. Characterization includes ESI- and ESI-TWIM-MS and TEM, along with 1D and 2D (1) H NMR spectroscopy.

Cellulose nanocrystals (CNC) isolated from bleached bagasse pulp were modified with a second-generation isocyanate dendron (G2-dendron) to prepare dendronized cellulose nanocrystals (DCN). Transmission electron microscopy (TEM), elemental analysis for nitrogen, Fourier transform infrared (FTIR) and 13C magic angle spinning nuclear magnetic resonance (13C MAS NMR) proved occurrence of the modification of cellulose nanocrystals surfaces. The dendronized cellulose nanocrystals were used as templates for formation of ZnS and CdS quantum dots with uniform diameter at low temperature in water. The prepared DCN/QDs were highly soluble in water. TEM images showed that the size of the prepared quantum dots was about 5 nm in diameter. UV-Visible and fluorescence spectroscopy showed absorption and emission at wavelength values lower than that reported for bulk ZnS and CdS.

Terpyridine-functionalized graphene oxides were prepared for self-assembly into 3D architectures with various metal ions (e.g., Fe, Ru). The resulting electrode materials showed significantly improved electroactivities for efficient energy conversion and storage. They showed promise for application in the oxygen reduction reaction (ORR), photocurrent generation, and supercapacitance.

An adamantane-based atom transfer radical initiator (Adm-Br) was prepared by the treatment of 1-[[N-[2-Hydroxy-l,l-bis(hydroxymethyl)ethyl]amino]carbonyl]adamantane with bromopropionyl bromide. The resulting initiator was subsequently used in the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) to form (Adm-p-MMA), which was successfully used, as a macroinitiator, in further ATRP reactions with 3-O-methacryloyl-1,2 5,6-di-O-isopropylidene-α-d-glucofuranose (gly), a glycomonomer, to afford the Adm-p-MMA-b-gly polymer. The new Adm-p-MMA-b-gly polymer subsequently was employed to form a nanocomposite with chitosan-modified, Nanofil clay (NC). The resulting Adm-p-MMA-b-gly/NC composite material was progressively hydrolyzed to regenerate the OH groups of the glucose units within the Adm-p-MMA-b-gly copolymer. The polymer/NC nanocomposites were characterized by X-ray diffraction, thermal gravimetric analysis, differential scanning calorimetry, and transmission electron microscopy. POLYM. ENG. SCI., 54:2669–2675, 2014. © 2013 Society of Plastics Engineers

Where there's a wheel, there's a way: The terpyridine-based title system has been synthesized through a facile self-assembly process. Two tris(terpyridine) ligands possessing angles of either 120° or 60° between adjacent tpy units were mixed with a stoichiometric amount of Zn(2+) (2:6:12) to generate the desired coordination-driven bicycle-like wheel (90 % yield).

A series of metallodendrimers 9–11, as well as their corresponding ligands, were designed and synthesized. These materials integrate perylene as a functional core with tpyRu II tpy termini; both chromophores are known for their photovoltaic properties. The products were fully characterized by a combination of 1 H NMR and 13 C NMR spec

We report the self-assembly and isolation of two metallamacromolecular constitutional isomeric pairs based on connectivity. Utilizing a robust dimer with varying substitution to the core benzene ring resulted not only in the isolation of the expected 60°-oriented tetramer and 120°-oriented hexamer but also in the unexpected isolation of a 60°-oriented hexamer and a 120°-oriented tetramer. These isomers were characterized by 1H NMR spectroscopy and mass spectrometry (ESI-travelling wave ion mobility), which revealed significant structural differences. Molecular modeling was utilized to aid in characterization.

The surface of Cloisite 30 B clay was treated with bromopropionyl bromide to form the clay Br-ended initiator needed for surface-initiated atom transfer radical polymerization (SI-ATRP). Several homo- and co-(SI-ATRP) polymerizations were conducted on the cured surface of the Cloisite 30 B clay using vinyl monomers, such as methyl methacrylate, styrene (St), and 2-(dimethylaminoethyl) methacrylate, along with the ligands 2,2′-bipyridine (bpy) and 1,1,4,7,10,10-hexamethyltriethylene tetraamine, and CuBr, as a catalyst. These grafted polymer–clay nanocomposites were characterized by X-ray diffraction, Thermal gravimetric analysis, differential scanning calorimetry, and Transmission electron microscopy. Most of the prepared nanocomposites displayed semi-exfoliated to exfoliated structures.

The preparation of multi-metallic Au nanocluster and nanowires has been achieved using terpyridine-based metallo-organic polymers as multi-ionic templates through a straightforward counterion exchange with aqueous NaAuCl4 followed by a mild reduction in-situ with sodium citrate. The mild reduction of the [TpyFeTpy]2+ x 2[AuCl4]- complex, derived from [TpyFeTpy]2+ x 2Cl- 1 (tpy = 2,2':6',2"-terpyridine), led to the formation of Au nanoclusters (Au NC) with diameters ranging from 7.5-88 nm. Each Au NC alone contained multiple nanoparticles, with diameters ranging from 2.5-4.5 nm. 1,4-bis-terpyridine based metallo-oraganic polymer [-TpyFeTpy-TpyFeTpy-]n(2n+) x [Cl]2n- 2 was found to generate a multi-ionic metallo-polymer with AuCl4- as the counterion, after mild reduction with sodium citrate, resulting in irregular zigzag shaped Au nanowires (Au NW). The prepared Au NW from the di-metallic complex 3 should find applications within electronic devices. Both Au NC and NW were also found to possess excellent catalytic properties.

Long chain (C16) alkylated metallocycles are synthesised and characterised. Their ordered aggregation was studied via TEM to gauge to the effects of molecular topology, solvent, counterion and metal centre(s) on morphology and nanoscale structure. The results indicate that their amphiphilicity significantly enhanced their self-ordering characteristics relative to controls and enabled the formation of nanoscale structures. Similar ordering was observed for both labile and non-labile analogues with SAXD showing comparable d-spacing values, suggesting the presence of intramolecular π–π stacking. Effect of counterion and solvent was studied with the non-labile system. Nanotubular, ribbon, or sheet-like structures were afforded depending upon conditions.

Two simple organic compounds, 5-nitroisophthalic acid (npa) and 4,4′-bipyridine (bpy), were used as building blocks for supramolecular self-assembly by hydrothermal synthesis. SEM, TEM, and XRD were used to analyse the multi-step assembly process in which npa and bpy assembled into nanotubes (or nanobelts) of about 30–100 nm in diameter and several millimetres in length and microtubes (or microbelts). The tubes then further assembled to form complex ordered structures, such as pom-pom-shaped and flower-like mesostructures. Hydrothermal-promoted, self-assembly of 5-nitroisophthalic acid and 4,4′-bipyridine generates nanotubes possessing a diameter of ~30–100 nm diameter and length of several millimeters as well as novel pom-pom- and flower-shaped mesostructures.

New metallomacrocycles composed of 2,2':6',2″-terpyridine (tpy) ligands and Ru(II) or Fe(II) transition metal ions were prepared by stepwise directed assembly and characterized by 2D diffusion NMR spectroscopy (DOSY), electrospray ionization traveling wave ion mobility mass spectrometry (ESI TWIM MS), and molecular modeling. The supramolecular polymers synthesized include a homonuclear all-Ru hexamer as well as heteronuclear hexamer and nonamer with alternating Ru/Ru/Fe metal centers. ESI MS yields several charge states from each supramacromolecule. If ESI is interfaced with TWIM MS, overlapping charge states and the isomeric components of an individual charge state are separated based on their unique drift times through the TWIM region. From experimentally measured drift times, collision cross-sections can be deduced. The collision cross-sections obtained for the synthesized supramacromolecules are in good agreement with those predicted by molecular modeling for macrocyclic structures. Similarly, the hydrodynamic radii of the synthesized complexes derived from 2D DOSY NMR experiments agree excellently with the radii calculated for macrocyclic architectures, confirming the ESI TWIM MS finding. ESI TWIM MS and 2D DOSY NMR spectroscopy provide an alternative approach for the structural analysis of supramolecules that are difficult or impossible to crystallize, such as the large macrocyclic assemblies investigated. ESI TWIM MS will be particularly valuable for the characterization of supramolecular assemblies not available in the quantity or purity required for NMR studies.

An approach to multicomponent coordination-driven self-assembly of the first terpyridine-based, shape-persistent, giant two-dimensional D(6h) supramacromolecular spoked wheel is reported. Mixing core T6, rim T3, and Zn(II) or Cd(II) ions in a stoichiometric ratio (1:6:12) permitted the selective generation of a highly symmetric spoked wheel in 94% isolated yield via geometric and thermodynamic control. The products were characterized by a combination of traveling-wave ion mobility mass spectrometry and NMR techniques together with TEM imaging, which agreed with computational simulations.

Construction of supramolecular architectures employing the self-assembly of predesigned building blocks has drawn considerable attention in the past decades. Based on the combinatorial library proposed by Lehn, self-assembling constructs are often an equilibrium distribution of possible assemblies possessing comparable stabilities. Assemblies with similar components resulting in an equilibrating mixture of binary or multiple entities have been reported. Under appropriate conditions, the thermodynamically most stable species can be obtained in quantitative yield. Based on these tenants, many successful strategies have been developed for the synthesis of metallocycles with triangular, rectangular, pentagonal, and hexagonal shapes. In contrast, few examples of larger polygonal structures are documented. Towards larger finite architectures, subtle variation of building blocks could result in a dramatic change to the final products. In the self-assembly of bis(terpyridine) ligands possessing a 1208 angle between two ligating moieties, only hexameric metallomacrocycles were previously reported due to the difficulty of separation and characterization. More recently, Newkome et al. successfully isolated unexpected pentameric and heptameric macrocycles from the Fe-mediated complexation of rigid bis(terpyridine) ligands. Herein, we employ kinetically stable (in which tpy=2,2’:6’,2’’-terpyridine, M=Fe and Ru) connectivity to afford a series of homoand heteronuclear metallomacrocycles by means of stepwise assembly procedures. By using metals that form strong coordinative bonds (Fe and Ru), the self-assembly process becomes kinetically controlled and irreversible, thus allowing for the formation of macrocycles other than the thermodynamically most stable hexameric ring. Further, the use of elongated bis(terpyridine) dimers as precursors introduces steric constraints and increased rotational freedom, which obstruct the formation of small metallocycles, while facilitating the construction of novel, large metallocycles that would be difficult to realize otherwise. Traveling-wave ion-mobility mass spectrometry (TWIM-MS) and molecular modeling provide unique insight into the distinct ring sizes formed and their conformational flexibility. Reaction (Scheme 1a) of 3,5-bis(4’-terpyridinyl)anisole (1) with 1.05 equivalents of FeCl2·4H2O in a mixed solvent of MeOH/CHCl3 at reflux for 18 h gave the pentamer (2 ; 6%), hexamer (3 ; 15%), and heptamer (4 ; 3%), which were isolated by column chromatography (SiO2) eluting with H2O/ MeCN/sat.-KNO3(aq) (1:12.5:1; v/v/v). Subsequently, the counterions were exchanged from NO3 to PF6 by adding a slight excess of methanolic NH4PF6 (1m). The H NMR spectrum (Figure S1a in the Supporting Information) of pentamer 2 displayed four sharp singlets at d=9.41 (3’,5’-tpyH), 8.61 (4-ArH), 8.16 (2,6-ArH) and 4.34 ppm (OCH3), supporting the presence of a single homogeneous environment for complexed bis(terpyridine) ligands, in contrast to linear oligomers that have more complicated patterns. Other supportive data included an expected upfield shift in the H NMR spectrum for the 6,6’’-tpyH protons (d=7.27 ppm, Dd= 1.48 ppm) relative to the corresponding peaks of ligand 1 and one sharp peak in the C NMR spectrum at d=57.3 ppm (OCH3). Its structure was further confirmed by the intense ESI-MS peaks (Figure S2a in the Supporting Information) at m/z 1382.7, 1000.4, 771.3, 618.6, 509.5, and 427.7, corresponding to [M nPF6] ions (n=3–8), respectively. The H NMR spectra of macrocycles 3 and 4 revealed similar patterns, but all aromatic peaks exhibited a slight downfield shift relative to the corresponding peaks in 2, presumably due to conformational changes in the larger rings. The 4-ArH signal in pentamer 2 showed a significant upfield shift (Dd= 0.13 ppm) in comparison with hexamer 3, owing to the shielding by the adjacent pyridines in the more crowded inner space (Figure S1b in the Supporting Information). A similar phenomenon was observed in our previous work. Heptamer 4 has more conformational flexibility, minimizing this shielding effect; its 4-ArH signal was shifted further downfield (Figure S1c in the Supporting Information). Macrocycles 3 (MW=5498.5 Da) and 4 (MW= 6414.9 Da) were further verified by their ESI mass spectra (Figure S2b and S2c in the Supporting Information). Hexamer 3 gave rise to eight major peaks at m/z 1229.7, 954.7, [a] Dr. Y.-T. Chan, Dr. X. Li, Dr. C. N. Moorefield, Prof. Dr. C. Wesdemiotis, Prof. Dr. G. R. Newkome Department of Polymer Science, Department of Chemistry The University of Akron, 170 University Circle-RM501B Akron, OH 44325-4717 (USA) Fax: (+1)330-972-2368 E-mail : newkome@uakron.edu wesdemiotis@uakron.edu Homepage: http://www.dendrimers.com [] Drs. Chan and Li contributed equally to this work. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201100559.

The construction of 2D or 3D materials using supramolecular chemistry principles has become an intriguing area of research. In particular, terpyridine-based building blocks have played a pivotal role in the construction of dimers, triangles, trigonal prisms, squares, 7–9] pentagons, and hexagons, based on their planar tridentate coordination mode and their facile potential for modification. Terpyridine (terpy) and its metal complexes are also of interest because of their well-known photophysical and electronic properties. Thus, the use of terpyridine for the construction of materials and molecular architectures with increasing complexity will continue to mature. However, the difficulty of obtaining single crystals suitable for X-ray structure determination means that other reliable techniques are essential for the characterization of macromolecular structures. Electrospray ionization (ESI) mass spectrometry has been applied in the identification and characterization under mild ionization conditions. In particular, the cold-spray (CSI) technique reported by Fujita and co-workers, and the Fourier transform mass spectrometry (FTMS) technique developed by Schalley and coworkers are the most prominent ESI-based methods. The work of Piguet and co-workers is also notable. Unfortunately, the signals that correspond to different charge states are superimposed and only a few isotope patterns of different charge states can be deconvoluted. Recently, traveling wave ion mobility mass spectrometry (TWIM-MS), a variant of ion mobility mass spectrometry (IM-MS), has been successfully applied to the detection and characterization of supramolecules. Ion-mobility-based separation enhances the resolving power of mass spectrometry by adding shapeand charge-dependent dispersion, which reduces isomer superposition and can deconvolute the isotope patterns of different charge states. Notably, isomeric linear and cyclic structures have been separated based on their different drift time in the ion mobility device. Herein, we report the 4,4’-bipyridine (bpy) assisted assembly of a hexagonal, dodeca Pd terpyridyl based macrocycle, and its characterization by NMR and TWIMMS. A recent example of the use of terpyridine and its Pd coordination for the formation of a metallocyclic rectangle was reported by Bosnich and co-workers, whereby two cofacially oriented, Pd terpyridine MeCN adducts were dimerized upon the addition of 4,4’-bipyridine. Our synthetic efforts began with an improved preparation of 1,3-bis(2,2’:6’,2’’-terpyridin-4’-yl)-5-tert-butylbenzene (1), which was isolated in 60% yield and exhibited identical H and C NMR spectra to that of the initially reported ligand. Ligand 1 was prepared by the reduction of commercially available 5-tert-butylbenzene-1,3-dicarboxylic acid with BH3·THF, followed by selective oxidation with pyridinium chlorochromate (PCC) and subsequent grinding with 2-acetylpyridine (4.05 equivalents) and NaOH to give an orange solid, which was then added to NH4OH and EtOH and heated at reflux for 24 hours. This ligand, which has coordination sites that are positioned 120 degrees apart, was treated with [Pd(MeCN)4](BF4)2 in dry MeCN to give [(1,3-bis(2,2’:6’,2’’-terpyridin-4’-yl)-5-tert-butylbenzene)Pd2(MeCN)2](BF4)4 2 in nearly quantitative yield (Scheme 1). Ligand 1 was initially insoluble in MeCN, but was readily solubilized when treated with [Pd(MeCN)4](BF4)2 in MeCN. The H NMR data confirmed the formation of adduct 2, with signals at d= 8.68 (s, 3’,5’-terpyH), 8.63-8.58 (m, 6,6’’-terpyH and 3,3’’-terpyH), 8.49 (t, 4,4’’-terpyH), and 7.89 ppm (t, 5,5’’terpyH); see Figure 1. A downfield shift of the tert-butyl singlet peak (from d= 1.51 to 1.57 ppm, Dd= 0.06 ppm) and the IR absorptions observed at 2334 and 2304 cm 1 assigned to the C N stretch also support the formation of a Pd adduct 2. [*] Dr. S. Perera, Dr. X. Li, Dr. M. Soler, A. Schultz, Prof. Dr. C. Wesdemiotis, Dr. C. N. Moorefield, Prof. Dr. G. R. Newkome Department of Polymer Science, Department of Chemistry, The University of Akron 302 Buchtel Common, Akron, OH 44325 (USA) Fax: (+1)330-972-2368 E-mail: wesdemiotis@uakron.edu newkome@uakron.edu Homepage: http://www.dendrimers.com [] These authors contributed equally to this work.

Since the advent of nanotechnology, a primary challenge has been to assemble materials from predesigned building blocks for the fabrication of nanometer-sized materials. Metal nanocrystals (NCs) have attracted significant attention due to their unique shape and size, as well as their tuneable electrical, optical and catalytic properties. A bottomup approach has generally been used for constructing the desired multi-unit composites from individual components. Although extensive studies have been performed on spherically shaped NCs, research on anisotropic nanoparticles, for example, nanorods (NRs) with a distinct 1D or linear structure, is limited. Since the properties of NCs are mostly sizeand shape-dependent, NRs have the potential to show novel as well as improved properties, such as in surface-enhanced Raman scattering (SERS) effects or optical and fluorescent properties, when compared to isotropic nanospheres (NSs). c,3] Geometrically, the aspect ratio (the length of major axis divided by the width of minor axis) of NRs is >1 and their cofacial assembly produces more angularly complex structures than that of the NSs. Side-to-side assemblies of NRs have been achieved by introducing active sites on the sides of the rods and subsequently connecting via DNA, electrostatic interaction, and more recently with click chemistry; however, arrangement of NRs in an endto-end orientation, for example, forming chains or branched structures, requires a regiospecific functionalization. Toward this goal, the tips of NRs have been modified with different metals, which were subsequently termed nanodumbbells, for participation in direct end-to-end assembly. It is well-known that Au NRs have different crystallographic facets, which comprise the ends and side surfaces. Recently, it was found that these side facets have a higher surface energy, and in turn, adsorb more bilayer surfactant, for example, cetyltrimethylammonium bromide (CTAB); notably, the yield of these surface-modified nanorods has been shown to be supplier (CTAB) dependent. Current progress on direct end-to-end Au NR assembly has focused on using biocompatible connectors, a,w-dithiols, and synthetic polymers. As well, organometallic connections, such as bis(terpyridine)-transition metal complexes, are also of interest due to their potential to impart unique electrical, optical, and photovoltaic properties. For example, hybrid Au NCs and bis(terpyridine)–Ru complexes have been fabricated and shown to exhibit enhanced electrochemical properties. Herein, we report the first example of a bottom-up approach for the end-to-end linear and branched assembly of Au NRs into multicomponent structures using [(disulfide-modified terpyridine)2–M ] (M=Fe or Cd) interconnectors and their facile disassembly and reassembly. The synthesis of disulfide-modified monoterpyridine (SStpy) 2, the [(SS-tpy)2–M ] complexes 3 (M=Fe), and 4 (M= Cd) is shown in Scheme 1. In a typical Gabriel synthesis, 4’(4-hydroxyphenyl)-2,2’:6’2’’-terpyridine was treated with N-(3-bromopropyl)phthalimide to afford the intermediate protected amine, which was subsequently deprotected (H2NNH2·H2O) to give the amine-modified monoterpyridine 1. The structure was supported (H NMR) by signals for the new OCH2 (4.17 ppm) and CH2NH2 (3.20 ppm) moieties; a dominate peak (ESI-MS) at m/z 383.3 [M+H] further confirms the structure. Disulfide-modified monoterpyridine 2 [a] Y.-T. Chan, Prof. Dr. G. R. Newkome Departments of Polymer Science and Chemistry The University of Akron, Akron, OH 44325-4717 (USA) Fax: (+1)330-972-2413 E-mail : newkome@uakron.edu [b] Dr. S. Li Excel Polymers, 14330 Kinsman Rd. Burton, OH 44325 (USA) [c] Dr. C. N. Moorefield Maurice Morton Institute for Polymer Science The University of Akron, Akron, OH 44325 (USA) [d] Dr. P. Wang ChemNano Materials, 2220 High St. Suite 605 Cuyahoga Falls, OH 44221 (USA) [e] Prof. Dr. C. D. Shreiner Chemistry Department, Hiram College, P.O. Box 67 Hiram, OH 44234 (USA) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201000040.

A new series of shape-persistent metallomacromolecules G0 and G1 as well as corresponding ligands, based on thiophene-functionalized bisterpyridine-Ru(II) with truxene moieties, as the nodes, were developed. All new compounds were fully characterized by (1) H, COSY, and (13) C NMR, as well as MALDI-TOF MS. Their photophysical properties revealed that the branched scaffold resulted in high molar absorption coefficients and broad absorption making these materials potential candidates for light-harvesting.

A study of the photovoltaic properties and performance for dye-sensitized solar cells using mesoporphyrin IX electrophoretically deposited on nanocrystalline TiO2 photoanodes is reported. Performance data obtained from these photovoltaic devices were compared with photocells having TiO2 films sensitized by dip-coating deposition in absence of electric field. Global conversion efficiencies achieved for the solar cells containing porphyrins electrophoretically deposited were 4 times higher than for cells containing porphyrins deposited by dip-coating. Preliminary results suggest that conversion efficiencies for these photovoltaic devices depend from the orientation acquired by the dye monolayers on the TiO2 surfaces.

A novel family of bis(terpyridinyl) ligands was designed and constructed by facile Pd-catalyzed coupling reactions. Subsequent terpyridine–transition-metal complexation facilitated self-assembly resulting in a hexagonal, trimeric series of metallomacrocycles. An enhanced solubility of a macrocycle and its bis(terpyridine) precursor possessing elongated, alkyl-branched phenylacetylene spacers was achieved by the incorporation of dodecyloxy moieties. The characterization of the metallomacrocycles included 1H, 13C NMR, and UV spectroscopy and mass spectrometry, as well as electrochemistry.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

5.1.2. Viscosity and Thermal Denaturation 1874 5.1.3. Induced Circular Dichroism 1875 5.1.4. Competitive Fluorescence Spectroscopy 1875 5.1.5. Closed Circular DNA 1876 5.1.6. Stereochemical Changes in DNA 1876 5.1.7. Site-Specific Intercalation 1877 5.1.8. Other Mononuclear Intercalators 1877 5.1.9. Multinuclear Intercalators 1878 5.2. Covalent Binding to Biomolecules 1881 5.3. Labeling Biomolecules 1882 5.4. Cytotoxicity 1885 5.4.1. Chemotherapeutic Agents 1886 5.4.2. Radiotherapeutic Agents 1892 6. Conclusion 1892 7. Acknowledgments 1892 8. References 1893

Adv. Mater. 2008, 20, 1381–1385 2008 WILEY-VCH Verlag G Non-covalent self-assembly via hydrogen bonding, van der Waals, and coordinative or ionic interactions have found widespread application enroute to supramolecular assemblies. Examples of ion-based materials include a molecular capsule made by two oppositely charged calixarenes, pseudorotaxanes accessed by ion-pair templation, polyelectrolyte-amphiphile monolayers, and ion-pair interactions between biomolecular recognition sites and their guests. Although these non-covalent associations are usually weaker and reversible when compared to most covalent interactions, ionically driven attractions exhibiting multiple interactions per specie can result in very strong binding energies. Incorporation of these interactions has also facilitated the construction of materials and devices for applications in photonics, electronics, conducting polymers, and polyelectrolytes. Herein, we report the ion-promoted, automorphogenic, and stoichiometric self-assembly of nanoscale composite fibers using a structurally rigid hexameric macrocycle [(112þ)(PF 6 )12] possessing photonic and electron storage potential and a dodeca carboxylate-terminated, 1 generation 1! 3 C-branched dendrimer [(2 )(Na)12] (Scheme 1). For comparison, the structurally related 3rd generation dendrimer [(3 ) (Na)108; Scheme 2], was treated with [(1 12þ)(PF 6 )12] to afford a neutral, sphere-like motif [(1)9(3)]m. These polyanionic dense-packed counterions led to ion pair superstructures in which the randomness of singly-charged counterions was eliminated. Numerous examples of these Ru-based cyclized metallomers have been reported. In this instance, meta-substituted bis(terpyridinyl)arene building blocks constructed with either hydrocarbon aliphatic chains or PEG-moieties were incorporated to increase the solubility of these selfassembled metallohexamers in organic or aqueous solutions, respectively. This solubility enhancement resulted in the increase of the yields of the macrocyclization products. Treatment of 3,5-[bis(terpyridinyl)]phenol with n-bromohexane using standard alkylation conditions (K2CO3, DMF) afforded a white microcrystalline ditopic ligand, which upon treatment with 1 equiv. of [Ru(Cl)2(DMSO)4], [36] gave (40–45%) of the desired hexaruthenium macrocycle [(112þ)(Cl )12]. Following counterion exchange by treatment with NH4PF6, the structure of [(112þ)(PF 6 )12] was confirmed ( H NMR) by observation of the characteristic triplet absorption at 4.50 ppm (ArCH2OCH2) and singlet at 9.28 ppm indicative of the 3 0,50-tpy protons. Its MALDI-TOF MS [m/z 6046.89 (Mþ 1PF 6 )] further confirmed the structure. Complex [(112þ)(PF 6 )12] exhibited significantly enhanced solubility in common organic solvents such as MeCN, acetone, DMSO, and CHCl3 in contrast to its corresponding methyl-substituted hexameric homolog. Pertinent dimensions of [(112þ)(PF 6 )12], based on molecular modeling studies, include a 17.5 A internal diameter void region and a 37.5 A overall diameter of the terpyridine lattice. The G1 dendrimer [(2 )(Na)12] was prepared by hydrolysis of the corresponding 12-tert-butyl ester with formic acid and was previously reported to possess a hydrodynamic diameter of 23.6 A at basic pH, as determined by 2D diffusion ordered spectroscopy (DOSY) NMR experiments. Notably, this diameter is larger than the internal void region diameter (17.5 A) of [(112þ)(PF 6 )12], which suggests that an ordered molecular packing would be predicated on the symmetrical association of the dendrimer smoothly fitting above and not entirely into the central cavity of the hexamer. The polycarboxylate [(2 )(Na)12] (2.2 mg, 1.4 mM) in MeOH and water was carefully layered on top of a deep red MeCN (10 ml) solution of [(112þ)(PF 6 )12] (8.5 mg, 1.4 mM) and allowed to set undisturbed at 25 8C for two weeks (Fig. 1) in a sealed vial. After several hours, the formation of a cotton-like fiber was observed, and after 12 days, the solution became completely colorless, indicative of a self-assembly process. The resultant red fibers were filtered and washed sequentially with MeCN (3 5 ml) then water (5 5 ml) to remove traces of starting materials, if present, and any inorganic salts. In comparison, mixing 12 equiv. of NaOAc and 1 equiv. of [(112þ)(PF 6 )12] under the identical conditions resulted in no

Pulsed gradient NMR techniques including diffusion-ordered NMR spectroscopy have been used to study the self-diffusion of three carboxylated dendrimers in aqueous solutions of neutral poly(vinyl alcohol) (PVA) and of cationic poly(allyl amine) (PAAm). The ionic interaction between the cationic PAAm network and the anionic dendrimers had the most significant effect on the diffusion of the dendrimers in the system. The self-diffusion coefficients of the dendrimers in PAAm were an order of magnitude lower than in PVA and more widely distributed, and the activation energy for the displacement of the dendrimers in PAAm was higher than that in PVA. The effects of the dendrimer size, polymer concentration, and temperature on the diffusion of the dendrimers have also been studied.