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Coordination-driven self-assembly of metal ions and organic ligands has been extensively applied over the past few decades, towards construction of various functional two-dimensional (2D) and three...

The reaction of a metallo-organic ligand (LA) in which two “V”-shaped bisterpyridines attaching to meta-position of “X”-shaped tetraterpyridine via connectivity and Zn2+ ions gave rise to 3D supramolecular architectures: octagram (Zn8LA4). However, a position varied ligand (LB) in which two “V”-shaped bisterpyridines locating at the ortho-position of “X”-shaped tetraterpyridine afforded a different 3D hexagram (Zn6LB3). Full characterizations included NMR (1H, 13C, 2D COSY, NOESY and DOSY), ESI-MS, TWIM-MS, TEM and AFM. The resulted structures were directly determined by the position of two “V”-shaped bisterpyridines attaching to “X”-shaped tetraterpyridine.

We synthesized a polythiophene with methyl-branched side chains, poly(3-2-methylpentylthiophene) (P3MPT), and studied the thermal properties, morphology, optoelectrical properties, and photovoltaic performance of P3MPT blended with the fullerene derivative, [6,6]-phenyl C₆₀-butyric acid methyl ester (PCBM). The results are compared to those of the commonly used poly(3-hexylthiopene) (P3HT) with linear side chains to investigate the effects of the methyl-branched side chain. Differential scanning calorimetry (DSC) shows a higher glass transition temperature, and both X-ray diffraction and UV–vis absorption reveal a lower crystallization rate for P3MPT as compared to P3HT, due to the methyl-branched side chains that more efficiently suppress the chain mobility. Such behaviors can create an optimal as well as a stable structure for bulk-heterojunction solar cells so that the P3MPT/PCBM-based device not only shows a higher power conversion efficiency (PCE) but can much more effectively maintain the efficiency with time than the P3HT/PCBM-based device does. The stable phase-separated structure in the P3MPT/PCBM blend is confirmed by the grazing-incidence small-angle X-ray scattering (GISAXS) technique, which explains the superior long-term stability of the P3MPT/PCBM solar cell.

Ligand patterns at the nanoscale are essential in modulating biological recognition and signaling through binding to receptor oligomers. Biocompatible nanoscaffolds that allow precise control of multiple ligand presentation would be of great use in manipulating cellular processes and understanding membrane receptor biology. We have previously developed tri-helix and tetra-helix macrocycle scaffolds based on the Pro9 peptide helix to control ligand arrangements that can selectively target receptor oligomers. A better understanding of the structure of these macromolecules would significantly reduce the difficulty in designing matching ligand positions for target receptors. In this work, we expand the arsenal of ligand patterns by preparing polyproline tri-helix macrocycle scaffolds of different sizes. These synthetic nanoscaffolds composed of peptide helices ranging from Pro6 to Pro12 also allowed us to systematically investigate their properties. With a combination of circular dichroism spectroscopy and ion mobility spectrometry-mass spectrometry (IMS-MS), the measurement for varied sizes of these scaffolds indicated the connecting dihedral angle between both ends of the helix affects the strain in the cyclic scaffold. The experimental collision cross section obtained from IMS-MS favors a propeller model for the helix arrangements. The results not only contribute conformational insights for the polyproline tri-helix system, but also provide precious information for the future design and synthesis of cyclic nanostructures based on peptide helices.

A two-ligand system composed of the predesigned multivalent and complementary terpyridine-based ligands was exploited to construct heteroleptic metallo-supramolecules and to investigate the self-assembly mechanism. Molecular stellation of the trimeric hexagon [Cd

Advances in polymer science have made polymers essential in our everyday life and have yielded unprecedented quantities of data over the past several decades. However, it is still challenging and i...

A metal-organic supramolecular nanobelt was synthesized by quantitative self-assembling terpyridine-functionized tetraphenylethylene (TPE) and Cd2+, which only showed a weak emission both in solution or aggregated state. Nevertheless, nanobelt complex could be transferred to a fluorescence turn-on sensor to S2- by taking advantage of the structural transformation from nanobelt to its fluorescent ligand.

Gigantic coordination molecules assembled from a large number of metal ions and organic ligands are structurally and functionally challenging to characterize. Here we show that a heterometallic clu...

Self-assembly of twelve pentatopic tectons, which have complementary edges or can be linked using either digonal or trigonal connectors, represents the optimal synthetic strategy to achieve spherical objects, such as chemical capsids. This process requires conditions that secure uninterrupted equilibria of binding and self-correction en route to the global energy minimum. Here we report the synthesis of a highly soluble, deca-heterosubstituted corannulene that bears five terpyridine ligands. Spontaneous self-assembly of twelve such tectons with 30 cadmium(II) cations produces a giant icosahedral capsid as a thermodynamically stable single product in high yield. Nuclear magnetic resonance (NMR) methods, mass spectrometry analyses, small-angle X-ray scattering, transmission electron microscopy, and atomic force microscopy indicate that this spherical capsid has an external diameter of nearly 6 nm and shell thickness of 1 nm, in agreement with molecular modeling. NMR and liquid chromatography evidences imply that chiral self-sorting complexation generates a racemic mixture of homochiral capsids., The icosahedron, as the polyhedron closest in symmetry to the sphere, is one of the most compelling Platonic solids for chemists to construct. Here, the authors assemble a supramolecular icosahedron from twelve pentatopic corannulene-based tectons, a strategy that was proposed over a decade ago but only now synthetically realized.

Nanosized cage-within-cage compounds represent a synergistic molecular self-assembling form of three-dimensional architecture that has received particular research focus. Building multilayered ultralarge cages to simulate complicated virus capsids is believed to be a tough synthetic challenge. Here, we synthesize two large double-shell supramolecular cages by facile self-assembly of presynthesized metal-organic hexatopic terpyridine ligands with metal ions. Differing from the mixture of prisms formed from the inner tritopic ligand, the redesigned metal-organic hexatopic ligands bearing high geometric constraints that led to the exclusive formation of discrete double-shell structures. These two unique nested cages are composed of inner cubes (5.1 nm) and outer huge truncated cubes (12.0 and 13.2 nm) with six large bowl-shape subcages distributed on six faces. The results with molecular weights of 75 232 and 77 667 Da were among the largest synthetic cage-in-cage supramolecules reported to date. The composition, size and shape were unambiguously characterized by a combination of 1H NMR, DOSY, ESI-MS, TWIM-MS, TEM, AFM, and SAXS. This work provides an interesting model for functional recognition, delivery, and detection of various guest molecules in the field of supramolecular materials.

Complementary complexation between 2,2&prime, 6&prime, 2&Prime, terpyridine (tpy) and 6,6&Prime, dianthracenyl-substituted tpy in the presence of Zn(II) ions provided an efficient strategy for construction of metallo-supramolecular diblock copolymers. To synthesize well-defined tpy-modified polystyrenes (PSs), an Fe(II) bis(tpy) complex bearing &alpha, bromoester as a metallo-initiator was applied to atom transfer radical polymerization (ATRP) to avoid poisoning the Cu(I) catalyst. Subsequently, a series of tpy-functionalized PSs was obtained after the decomplexation of &lt, tpy-Fe(II)-tpy&gt, junction by tetrakis(triethylammonium) ethylenediaminetetraacetate (TEA-EDTA) under mild conditions. The metallo-supramolecular poly(3-hexylthiophene) (P3HT)-block-PS diblock copolymers were prepared by simply mixing the corresponding terminally tpy-modified homopolymers with Zn(II) ions, and further characterized by 1H NMR and diffusion ordered spectroscopy (DOSY) experiments. The approach using metallo-initiators for ATRP offers an opportunity to construct tpy-functionalized polymers with controllable molecular weights and low polydispersities. Through the spontaneous heteroleptic complexation, a variety of metallo-supramolecular diblock copolymers with tunable block ratios can be easily constructed.

Based on the predesigned self-selective complexation, metallo-supramolecular P3HT-b-PEO diblock copolymers with varying block ratios were synthesized, and their oriented polymer films generated during solvent evaporation in a 9 T magnetic field were investigated. An anisotropic, ordered layer structure was achieved using [P3HT20 -Zn-PEO107 ] and carefully characterized by polarized optical microscopy (POM), AFM, polarized UV/Vis spectroscopy, and GI-SAXS/WAXS. The PEO-removed [P3HT20 -Zn-PEO107 ] film was obtained after decomplexation with TEA-EDTA under mild conditions, and the selective removal of PEO domains was evidenced by UV/Vis and ATR-FTIR spectroscopy. Anisotropic photoconductivity of the magnetically aligned film was evaluated by flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements. The results indicated that the presence of insulating crystalline PEO segments diminished the photoconductivity along the P3HT backbone direction.

We report here that energy migration during luminescence can be extremely minimized by caging the fluorescent centers in a molecular cluster of [Tb6(μ3-F)8(piv)10(Hpiv)4DMF]·xDMF·yH2O 1. Experimental and theoretical simulations reveal that bonding terbium with fluoride is the key to reducing the non-radiative multi-phonon relaxation processes, which is disparate to the common hydroxy-based lanthanide clusters.

‘Aniono’ double helicates and grids were constructed using PO43– anions and a bis–tris(urea) ligand and interconverted by changing the counter-cation., Supramolecular assembly of well-defined discrete architectures has been of great interest due to the tunable properties of these structures in functional materials and bio-mimicking. While metal-coordination-driven assembly has been extensively studied, anion-coordination-driven assembly (ACDA) is just emerging for constructing complex supramolecular structures. Herein two A2nL2n (A = anion, L = ligand; n = 1 or 2) ‘aniono’-supramolecular assemblies, i.e. double helicates and the first anion grid, have been constructed based on the coordination between phosphate (PO43–) anion and a bis–tris(urea) ligand. Moreover, the aniono-grid and double helicate motifs can be readily interconverted under ambient conditions by simply changing the counter-cation. These results redefine the power and scope of ACDA, which may represent a new approach in the assembly of well-defined architectures in parallel with the metal coordination-driven assembly of metallo-supramolecules.

Tetrafunctionalized calix[4]resorcinarene cavitands commonly serve as supramolecular scaffolds for construction of coordination-driven self-assembled capsules. However, due to the calix-like shape, the structural diversity of assemblies is mostly restricted to dimeric and hexameric capsules. Previously, we reported a spontaneous heteroleptic complexation strategy based on a pair of self-recognizable terpyridine-based ligands and CdII ions. Building on this complementary ligand pairing system, herein three types of nanocapsules, including a dimeric capsule, a Sierpinski triangular prism, and a cubic star, could be readily obtained through dynamic complexation reactions between a tetratopic cavitand-based ligand and various multitopic counterparts in the presence of CdII ions. The dimeric capsular assemblies display the spacer-length-dependent self-sorting behavior in a four-component system. Moreover, the precise multicomponent self-assembly of a Sierpinski triangular prism and a cubic star possessing three and six cavitand-based motifs, respectively, demonstrates that such self-assembly methodology is able to efficiently enhance architectural complexity for calix[4]resorcinarene-containing metallo-supramolecules.

We present a series of tripodal ligands L1–3, which fold into hemicages C1–3 by using coordination-driven dynamic combinational chemistry. The identities of these hemicages were characterized using 1H NMR, 1H–1H COSY, DOSY, and ESI-TWIM-MS. Free rotation of the ferrocene structural units in the ligands affords an adaptable directionality, which is essential for the construction of these hemicages. Encapsulation of adamantane by C2 indicates the presence of a well-defined inner cavity as the binding pocket.

An anion-coordination-based A(4)L(6) ("A" denotes anion and "L" is ligand) tetrahedral cage was constructed by a C-2-symmetric bis-bis(urea) ligand and phosphate anion, which showed reversible interconversion with the A(2)L(3) triple helicate as a response to the template, concentration, or solvent. Notably, an unusual "peripheral" templation was found to be critical to stabilize the tetrahedral structure. This peripheral effect was utilized to assemble an "empty" A(4)L(6) cage that allows the multi-stimuli-controlled capture/release of biologically important species such as choline and acetylcholine.

Upon treatment with ZnII ions, a series of BINOL-bridged bis(phenanthroline) ligands was self-assembled into [M2L3] metallocages, which were carefully characterized by NMR spectroscopy and ESI-MS spectrometry. Among them, a racemic mixture of the BINOL-bridged bis(phenanthrolines) underwent chiral self-sorting to afford two homochiral metallocages. The narcissistic self-sorting process of the metallocages was observed in the complexation reaction of the constitutionally isomeric bis(phenanthrolines) with varying connection positions. Moreover, the endo hydroxyl-functionalized metallocage [Zn2{(S)-L2OH}3] exhibited catalytic activity and substrate selectivity for the Knoevenagel condensation reactions of aromatic tricarbaldehydes with malononitrile.

A novel metal–organic ligand (MOL 2) has been prepared by linking two V-shaped bis-terpyridines with one X-shaped tetrakis-terpyridine through the stable connectivity. The complexati...

A series of stellated metallosupramolecular architectures have been assembled through three-component integrative self-sorting. Building on the complementary ligand pairing, the initial attempts to synthesize the hexagram complex from a combination of X-shaped

A shape-persistent metallosupramolecular multirhomboid that inlays a hexarhomboid polygon in a three-lobed flat structure was prepared by means of coordination-driven self-assembly. The key ligands were synthesized by a "reaction on complex" strategy that becomes accessible to troublesome metalloorganic ligand L3. The formation here consists of four different starting components and two metal ions. Complementarity of the shape and size drives molecular puzzling and results in the multicomponent, quantitative self-assembled construct.

Three heterobimetallic metallomacrocycles were readily assembled through either a stepwise or a one-pot protocol by selective complexation of ZnII ions and PdII or PtII acceptors with the predesigned ligands possessing one 60°-bent bisterpyridine and two mono- or bis-pyridines. In the multicomponent self-assembly, the preorganized ZnII-terpyridine metallo-triangle led to the formation of the exterior macrocycles.

The intricate discrete supramolecular architectures via two or more noncovalent interactions are very attractive for chemists. In this paper, a series of homomeric metallo-supramolecular lemniscates were prepared in nearly quantitative yields by assembling either dialkylammonium salt- or benzo-21-crown-7 (B21C7)-containing terpyridyl metallo-organic ligands with Zn2+. Furthermore, the heteromeric analogue could be obtained through two ways: (1) the cooperative interaction of coordination-driven self-assembly and host-guest recognition and (2) the transformation from homodimers to heterodimers driven by host-guest interaction. These supramolecules were characterized by nuclear magnetic resonance (NMR), diffusion-ordered NMR spectroscopy, electrospray ionization mass spectrometry, and two-dimensional (2D) ion-mobility mass spectrometry.

Predesigned complementary complexation of two 2,2':6',2″-terpyridine-based ligands was established by installing 2,6-dimethoxyphenyl substituents at the terpyridyl 6,6″-positions, which provided ancillary ion-dipole interactions in the coordination process and extra π-stacking stabilization in the resultant heteroleptic complex. The high-fidelity self-recognition ligation afforded facile access to the quantitative self-assembly of multicomponent triangle [Cd6L(3)3L(4)3] and ditrigon [Cd15L(3)6L(5)3] (that is, a hexagon with six 120° angles and two alternating edge lengths). It was found that the linear 6,6″-substituted ditopic motif (L(3)) would be directed by the ligand geometry of L(5) to selectively incorporate into the parallel homoleptic connections in the bilayered framework.

Construction of 3D terpyridine-based metallopolyhedra remains challenging because of the linear coordination geometry of ⟨tpy-MII-tpy⟩ connectivity. A progressive strategy is made by assembling tetranuclear terpyridyl metal–organic ligands to afford a novel regular octahedron, whose structure was established by NMR, electrospray ionization mass spectrometry, traveling-wave ion-mobility mass spectrometry, atomic force microscopy, and transmission electron microscopy. This strategy provides an efficient method for the construction of 3D terpyridine-based metallopolyhedra.

The amalgamation of different components into a giant and intricate structure that makes quantitative and spontaneous assembly through molecular design is indispensable but challenging. To construct novel metallo-supramolecular architectures, here we present an architectural design principle based on multicomponent self-assembly. Using a carefully designed hexatopic terpyridine-based metallo-organic ligand (MOL), [Ru2T2K], we report on the formation of supramolecular trapezoid Zn5[Ru2T2K]V2, hollow hexagon Zn15[Ru2T2K]3K3, and giant star-shaped supramolecule Zn18[Ru2T2K]3[Ru2X2V]3, all of which were assembled by one-pot, nearly quantitative assembly of [Ru2T2K] with the ditopic 60°-directed bisterpyridine V, tetrakisterpyridine K, and MOL [Ru2X2V], respectively. The complementary ligands were selected on the basis of the size- and shape-fit principles, actually similar to the mortise–tenon joint that aligns and locks the two complementary wood components. This strategy is expected to open the door to soph...

Metal-ligand coordination and host-guest recognition are introduced into the hybrid system in order to prepare supramolecular gels, which can be responsive to multiple external stimuli such as metal ions, competitive guest/host molecules, and oxidants. To this end, the triangular terpyridine-based metallocycles functionalized with 1-adamantyl and ferrocenyl groups are constructed through self-assembly, and further used as supramolecular cross-linkers for gelation of β-CD-containing copolymers. Their gelation and stimuli-response tests are discussed, and an application of the metallotriangles for serving as supramolecular glue is demonstrated through a series of adhesion experiments. This approach enables facile access to construction of multifunctional metallosupramolecules as well as functional hybrid materials.

Supramolecular diblock copolymers using metal-ligand coordination can be synthesized under ambient conditions by delicate design of the end groups of the homopolymer chains. However, mass spectrometric analysis of such metallo-supramolecular copolymers is challenging. One of the reasons is the nonpolarity of the polymer chains, making it hard to disperse the complexes in electrospray ionization (ESI)-friendly environments. The other difficulty is the noncovalent nature of such copolymers, which is easily disrupted during the ionization. Here, we demonstrate that the intact metallo-supramolecular diblock copolymers can be maintained sufficiently during the ESI process in aqueous solution within micelles. The high-resolution mass spectrometric evidence revealed that the surfactant molecules effectively protect the noncovalent binding of the complexes into gaseous ions. Intriguingly, surfactant molecules were sufficiently detached away from the copolymer complexes, giving unambiguous mass spectra that were predominated by intact diblock copolymers. This ESI-based approach allowed us to investigate the relative bond strengths of metal-to-ligand complexation using collision-induced dissociation (CID) in the ion trap mass spectrometry. Conformational features and collision cross sections of the copolymers were thus obtained using subsequent ion mobility spectrometry mass spectrometry (IMS-MS). Remarkable environment-dependent conformations of the denoted diblock copolymers were found using this mass spectrometric platform.

Spontaneous formation of the heteroleptic cadmium(II) bis(terpyridine) complex under ambient conditions can be achieved by a combination of 6,6''-di(2,6-dimethoxylphenyl)-substituted and unsubstituted terpyridine-based ligands. Building on this dynamic heteroleptic complexation, diverse metallo-supramolecular macrocycles and cages were readily assembled in quantitative yields from the predesigned multicomponent systems. The complementary ligation reinforced self-recognition to facilitate the shape-dependent self-sorting of a four-component dynamic library into two well-defined parallelograms. In addition, the subtle lability difference between homoleptic and heteroleptic complexes led to the site-selective CdII -ZnII transmetalation in the Sierpinski triangle. Facile construction of a dodecanuclear tetrahedral metallocage was also realized by using two self-recognizable tritopic building blocks. The photophysical study of the metallo-supramolecules assembled from the d10 metal ions revealed intense ligand-based photoluminescence in solution. The self-assembly strategy described here provides an efficient methodology for building pre-programmable, sophisticated supramolecular architectures furnished with photoactivity.

A series of metallo-supramolecular ring-in-ring structures was generated by assembling Cd(II) ions and the multivalent terpyridine ligands (L(1-3)) composed of one 60°-bent and two 120°-bent bis(terpyridine)s with varying alkyl linker lengths. The mechanistic study for the self-assembly process excluded an entropically templated pathway and showed that the intramolecularly complexed species is the key intermediate leading to ring-in-ring formation. The next-generation superstructure, a spiderweb, was produced in quantitative yield using the elongated decakis(terpyridine) ligand (L(5)).

The combination of conventional transition-metal-catalyzed coupling (2 e- process) and photoredox catalysis (1 e- process) has emerged as a powerful approach to catalyze difficult cross-coupling reactions under mild reaction conditions. Reported is a palladium carbodicarbene (CDC) complex that mediates both a Suzuki-Miyaura coupling and photoredox catalysis for C-N bond formation upon visible-light irradiation. These two catalytic pathways can be combined to promote both conventional transition-metal-catalyzed coupling and photoredox catalysis to mediate C-H arylation under ambient conditions with a single catalyst in an efficient one-pot process.

One of the pathologic hallmarks in Alzheimer's disease (AD) is extracellular senile plaques composed of amyloid-β (Aβ) fibrils. Blocking Aβ self-assembly or disassembling Aβ aggregates by small molecules would be potential therapeutic strategies to treat AD. In this study, we synthesized a series of rationally designed divalent compounds and examined their effects on Aβ fibrillization. A divalent amide (2) derived from two molecules of caffeic acid with a propylenediamine linker of ∼5.0 A in length, which is close to the distance of adjacent β sheets in Aβ fibrils, showed good potency to inhibit Aβ(1–42) fibrillization. Furthermore, compound 2 effectively dissociated the Aβ(1–42) preformed fibrils. The cytotoxicity induced by Aβ(1–42) aggregates in human neuroblastoma was reduced in the presence of 2, and feeding 2 to Aβ transgenic C. elegans rescued the paralysis phenotype. In addition, the binding and stoichiometry of 2 to Aβ(1–40) were demonstrated by using electrospray ionization−traveling wave ion mobility−mass spectrometry, while molecular dynamic simulation was conducted to gain structural insights into the Aβ(1–40)−2 complex.

Self-assembly of a metallo-organic ligand, composed of an inner uncomplexed 120°-bis(terpyridine) and an outer extended free 120°-bis(terpyridine) linked with a triple connector, with Zn2+, gave rise to a discrete planar supramolecular honeycomb patterned fractal. The central metallo-hexagon was surrounded by six identical metallo-hexagons which perfectly mimicked the natural simplest honeycomb structure.

Complementary coordination of two predesigned 2,2′:6′,2″-terpyridine-based ligands to a ZnII ion led to the exclusive formation of a heteroleptic bis(terpyridine) complex under ambient conditions. This highly self-selective process was facilitated by 9-anthracenyl substituents at the 6,6″-positions of a terpyridine, which not only decelerated the formation rate of its homoleptic complex, but also provided π-stacking stabilization in the heteroleptic complex. Facile construction of metallo-supramolecular poly(3-hexylthiophene) (P3HT)-block-poly(ethylene oxide) (PEO) diblock copolymers was realized using the complementary ligand pair. The morphological studies of the amphiphilic block copolymers in solution were conducted by atomic force microscopy and transmission electron microscopy, indicating that the self-assembled core–shell morphology such as spherical and fibrillar nanostructures could be controlled by adjusting the rod–coil block ratios. The heteroleptic complexes residing at the junction between t...

How to orient polymers homeotropically in thin films has been a long-standing issue in polymer science because polymers intrinsically prefer to lie down. Here we provide a design principle for polymers that are processable into a 2D homeotropic order. The key to this achievement was a recognition that cylindrical polymers can be designed to possess oppositely directed local dipoles in their cross-section, which possibly force polymers to tightly connect bilaterally, affording a 2D rectangular assembly. With a physical assistance of the surface grooves on Teflon sheets that sandwich polymer samples, homeotropic ordering is likely nucleated and gradually propagates upon hot-pressing towards the interior of the film. Consequently, the 2D rectangular lattice is constructed such that its b axis (side chains) aligns along the surface grooves, while its c axis (polymer backbone) aligns homeotropically on a Teflon sheet. This finding paves the way to molecularly engineered 2D polymers with anomalous functions., Vertical alignment of polymers on surfaces is challenging due to their flexibility and tendency to arrange on horizontal planes. Here, the authors report a design principle allowing polymers to be arranged into 2D homeotropic orientations by using long-range dipole-dipole interactions and hot-pressing on Teflon sheets.

Two hexanuclear metalloprisms possessing three dibenzo[24]crown-8 units were generated in quantitative yields by complexation of the predesigned tetratopic 2,2′:6′,2′′-terpyridine ligand (T) with CdII and ZnII ions, respectively. The prismatic hosts were subsequently self-assembled with the trifunctional guest molecule (TriG) containing dibenzylammonium ions to afford the corresponding metallo-supramolecular pseudo-suit[3]anes. It was serendipitously found that the host–guest inclusion rates could be modulated by the subtle dynamic difference in metal–ligand frameworks, finally leading to a selective encapsulation event in the presence of both metallo-suits.

The self-assembly of Zn(II) ions and bis(terpyridine) (tpy) ligands carrying 120° or 180° angles between their metal binding sites was utilized to prepare metallosupramolecular libraries with thetpy-Zn(II)-tpyconnectivity. These combinatorial libraries were separated and characterized by ion mobility mass spectrometry (IM MS) and tandem mass spectrometry (MS(2)). The 180°-angle building blocks generate exclusively linear complexes, which were used as standards to determine the architectures of the assemblies resulting from the 120°-angle ligands. The latter ligand geometry promotes the formation of macrocyclic hexamers, but other n-mers with smaller (n = 5) or larger ring sizes (n = 7-9) were identified as minor products, indicating that the angles in the bis(terpyridine) ligand and within the coordinative tpy-Zn(II)-tpy bonds are not as rigid, as previously believed. Macrocyclic and linear isomers were detected in penta- and heptameric assemblies; in the larger octa- and nonameric assemblies, ring-opened conformers with compact and folded geometries were observed in addition to linear extended and cyclic architectures. IM MS(2) experiments provided strong evidence that the macrocycles present in the libraries were already formed in solution, during the self-assembly process, not by dissociation of larger complexes in the gas phase. The IM MS/MS(2) methods provide a means to analyze, based on size and shape (architecture), supramolecular libraries that are not amenable to liquid chromatography, LC-MS, NMR, and/or X-ray techniques.

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.

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.

Traveling wave ion mobility mass spectrometry (TWIM MS) was combined with gradient tandem mass spectrometry (gMS(2)) to deconvolute and characterize superimposed ions with different charges and shapes formed by electrospray ionization (ESI) of self-assembled, hexameric metallomacrocycles composed of terpyridine-based ligands and Cd(II) ions. ESI conditions were optimized to obtain intact hexameric cation assemblies in a low charge state (2+), in order to minimize overlapping fragments of the same mass-to-charge ratio. With TWIM MS, intact hexameric ions could be separated from remaining fragments and aggregates. Collisional activation of these hexameric ions at varying collision energies (gMS(2)), followed by TWIM separation, was then performed to resolve macrocyclic from linear hexameric species. Because of the different stabilities of these architectures, gMS(2) changes their relative amounts, which can be monitored individually after subsequent ion mobility separation. On the basis of this unique strategy, hexameric cyclic and linear isomers have been successfully resolved and identified. Complementary structural information was gained by the gMS(2) fragmentation pattern of the metallosupramolecules, acquired by collisionally activated dissociation after TWIM dispersion. TWIM MS interfaced with gMS(2) should be particularly valuable for the characterization of a variety of supramolecular polymers, which often contain isomeric architectures that yield overlapping fragments and aggregates upon ESI MS analysis.

Femtosecond time-resolved absorption spectroscopy has been used to study the excited-state charge transfer dynamics in a set of self-assembled cyclic Fe(II)-bisterpyridine compounds with different π-conjugated ligands. By analyzing the dynamics, the internal conversion process involving a ligand-centered π-π* state to a lower lying metal-to-ligand charge transfer (MLCT) state was investigated. This is followed by intersystem crossing to the lowest MLCT state, which was found to occur at the ∼100 fs time scale. Vibrational cooling in the lowest MLCT state was found to occur on the 10s of femtoseconds time scale. The lowest MLCT state had an excited-state lifetime longer than 5 ns, indicating the possibility of light-induced excited-state spin trapping (LIESST).

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.

Highly ordered mesoporous silicas with large accessible pores have been prepared by using pre-synthesized poly(ethylene oxide)- b -poly(methyl acrlyate) (EO n MA m ) diblock copolymers as templates. Via adjusting the chain length of EO versus that of MA, a series of silica mesostructures, including two-dimensional (2-D) hexagonal, 3-D bicontinuous ( Ia3d ), and body-centered cubic ( Im3m ) symmetries, were prepared with the use of tetraethyl-orthosilicate (TEOS) as the silica precursor under acidic conditions. The mesostructures of all materials were characterized by small-angle X-ray scattering and transmission electron microscopy measurements. N 2 adsorption–desorption isotherms reveal that the pore size ranges from 4 to 30 nm with a narrow pore-size distribution and its dimension is proportional to the chain length of MA units.

Three unsymmetrical, 60°-bended bisterpyridine ligands with varying phenylene spacer lengths have been synthesized via the Suzuki-Miyaura coupling reactions. Their self-assembly processes were found to be strongly dependent on the ligand geometry. Upon complexation with Zn(II) ions, only 2,4''-di(4'-terpyridinyl)-1,1':4',1''-terphenyl underwent self-selection to give a trinuclear metallomacrocycle with perfect heteroleptic connectivity and the other two afforded a mixture of constitutional isomers. The metallosupramolecular assemblies were characterized by NMR spectroscopy, electrospray mass spectrometry (ESI MS), and single-crystal X-ray diffraction. In particular, the identification of isomeric architecture was accomplished using tandem mass spectrometry (MS(2)) coupled with traveling wave ion mobility mass spectrometry (TWIM MS).