Dendritic and Ion-Pairing Effects in Oxo-anion Recognition by Giant Alkylferrocenyl Dendrimers

Ferrocene-Bearing Dodecylphthalocyanines: Synthesis, Spectroscopic and Electrochemical Behavior

Ferrocenylbutoxy-bearing dodecylated phthalocyanines, MPc(C₁₂H₂₅)_x(OC₄H₈Fc)_y with M = 2H (compound series 6 and 8) or Zn (compound series 5, 7 and 9), x ≤ 8 and y ≤ 4, were synthesized through either metal-free statistical condensation between 3,6-bis(dodecyl)phthalonitrile, 2, and 4- (1), or 3-(4'-ferrocenylbutoxy)phthalonitrile, 4, or a zinc template statistical condensation between 4,5-bis(dodecyl)phthalonitrile, 3, and 1 in the presence of anhydrous zinc acetate, or by zinc insertion into metal-free phthalocyanines. Compounds were designed to have eight nonperipheral dodecyl substituents, six nonperipheral dodecyl, either one peripheral or one nonperipheral 4'-ferrocenylbutoxy substituent, four nonperipheral dodecyl and two peripheral 4'-ferrocenylbutoxy substituents, or four peripheral 4'-ferrocenylbutoxy substituents. The compound having six peripheral dodecyl and one peripheral 4'-ferrocenylbutoxy substituents was also synthesized. Metal-free and zinc complex Q-band maximum absorption wavelengths increased nonlinearly from 704 to 725 nm for the Q_y-band of metal-free compounds, or from 676 to 699 nm for the Q-band of zinc complexes in moving from all peripheral-substituted to all non-peripheral-substituted complexes. A rare case of accidental Q-band degeneracy where only one electronic Q-band is observed for asymmetrical zinc complexes NOT having D_4h symmetry, compounds 5, 7b-e, and 9b, is also described. X-ray photoelectron spectroscopy (XPS) differentiated between four types of phthalocyanine nitrogen atoms; binding energies were ca. 399.8 (N-H), 398.1 (N_meso), 397.8 (N_core), and 398.7 eV (N-Zn), respectively. An electrochemical study of these compounds revealed up to five different redox processes in dichloromethane but only three in tetrahydrofuran (THF). The first ring-based oxidation of both metal-free compounds 6a-e and zinc phthalocyanines 7a-e exhibited a near-linear increase in peak anodic potentials, E_pa, with the systematic replacement of two nonperipheral dodecyl substituents with one peripheral 4'-ferrocenylbutoxy group. When four 4'-ferrocenylbutoxy groups were substituted on the phthalocyanine macrocycle, aggregation of the first oxidized species was observed. Zinc insertion into metal-free phthalocyanines lowered formal redox potentials. An electrochemical scheme consistent with electrochemical results is provided.

Controlled Anchoring of (Phenylureido)sulfonamide-Based Receptor Moieties: An Impact of Binding Site Multiplication on Complexation Properties

The repetition of urea-based binding units within the receptor structure does not only lead to monomer properties multiplication. As confirmed by spectroscopic studies, UV-Vis and 1H-NMR in classical or competitive titration mode, the attachment to a carrier allocates the active moieties to mutual positions predetermining the function of the whole receptor molecule. Bivalent receptors form self-aggregates. Dendritic receptors with low dihydrogen phosphate loadings offer a cooperative complexation mode associated with a positive dendritic effect. In higher dihydrogen phosphate concentrations, the dendritic branches act independently and the binding mode changes to 1:1 anion: complexation site. Despite the anchoring, the dendritic receptors retain the superior efficiency and selectivity of a monomer, paving the way to recyclable receptors, desirable for economic and ecological reasons.

The comparison of structure, nature of bond, and electronic transitions in [M(η5 -Cp)(η5 -C60 Me5 )] (M = Fe2+ , Ru2+ , Os2+ ) hybrids and corresponding metallocenes; a theoretical study

In this paper, metallocene-fullerene hybrid complexes, [M(η⁵ -Cp)(η⁵ -C₆₀ Me₅ )] (M = Fe²⁺ , Ru²⁺ , Os²⁺ ), as well as corresponding classical metallocenes have been studied theoretically at BP86/def2-SVP and M06L/def2-SVP levels of theory. With considering these metal complexes as an ABA' system (B is the central metal ion and A and A' are related η⁵ -ligands), the total interaction energies were calculated using common methods, as well as by calculating the interaction energies between the four defined pairs of fragments including A-B, B-A', A-BA', and AB-A'. The resulting data clearly showed that in all complexes there is a strong anticoopertivity between two metal-(η⁵ -ligand) bonds. In order to understand the origin of difference in values of various calculated interactions in above two types of complexes, the nature of metal-ligand bonds was also studied using energy decomposition analysis-natural orbital for chemical valence calculations. The results showed that in hybrid complexes, in contrast to metallocenes, the orbital interactions are considerably larger than electrostatic interactions.

Electrochemical Anion Sensing: Supramolecular Approaches

Anions play a vital role in a broad range of environmental, technological, and physiological processes, making their detection/quantification valuable. Electroanalytical sensors offer much to the selective, sensitive, cheap, portable, and real-time analysis of anion presence where suitable combinations of selective (noncovalent) recognition and transduction can be integrated. Spurred on by significant developments in anion supramolecular chemistry, electrochemical anion sensing has received considerable attention in the past two decades. In this review, we provide a detailed overview of all electroanalytical techniques that have been used for this purpose, including voltammetric, impedimetric, capacititive, and potentiometric methods. We will confine our discussion to sensors that are based on synthetic anion receptors with a specific focus on reversible, noncovalent interactions, in particular, hydrogen- and halogen-bonding. Apart from their sensory properties, we will also discuss how electrochemical techniques can be used to study anion recognition processes (e.g., binding constant determination) and will furthermore provide a detailed outlook over future efforts and promising new avenues in this field.

Diaqua-β-octaferrocenyltetraphenylporphyrin: a multiredox-active and air-stable 16π non-aromatic species

Herein the synthesis and properties of the first β-octaferrocenyltetraphenylporphyrin, {TPPFc₈(H₂O)₂}, in its extraordinary stable and non-aromatic 16π form are reported, showing seven separate reversible redox events.

Anion Recognition in Water: Recent Advances from a Supramolecular and Macromolecular Perspective

The recognition of anions in water remains a key challenge in modern supramolecular chemistry, and is essential if proposed applications in biological, medical, and environmental arenas that typically require aqueous conditions are to be achieved. However, synthetic anion receptors that operate in water have, in general, been the exception rather than the norm to date. Nevertheless, a significant step change towards routinely conducting anion recognition in water has been achieved in the past few years, and this Review highlights these approaches, with particular focus on controlling and using the hydrophobic effect, as well as more exotic interactions such as C-H hydrogen bonding and halogen bonding. We also look beyond the field of small-molecule recognition into the macromolecular domain, covering recent advances in anion recognition based on biomolecules, polymers, and nanoparticles.

Fabrication of a label-free electrochemical immunosensor using a redox active ferrocenyl dendrimer

An amperometric immunosensor based on a redox active ferrocenyl end-grafted PAMAM dendrimer provides highly sensitive detection of immunoglobulin, down to 2 ng mL⁻¹.

Functional Materials Based on Metal-Containing Polymers

Since the dawn of human civilization, there has been a demand for materials that include ceramics, metals, and polymers. Increasing demand as well as the need for enhanced performance has driven material scientists to research metal-containing polymers as complements of these materials. Consequently, metal-containing polymers that integrate the excellent thermal, electronic, optical, and magnetic properties of metals with the lightweight, low cost, and in some cases, the chemical stability of organic-based polymers have been designed, and used as catalysts, sensors, ceramic precursors, magnetic materials, and electrical conductors. This chapter provides an overview of some of these functional metal-containing polymers.

Sandwich complex-containing macromolecules: property tunability through versatile synthesis

Sandwich complexes feature unique properties as the physical and electronic properties of a hydrocarbon ligand or its derivative are integrated into the physical, electronic, magnetic, and optical properties of a metal. Incorporation of these complexes into macromolecules results in intriguing physical, electrical, and optical properties that were hitherto unknown in organic-based macromolecules. These properties are tunable through well-designed synthetic strategies. This review surveys many of the synthetic approaches that have resulted in tuning the properties of sandwich complex-containing macromolecules. While the past two decades have seen an ever-growing number of research publications in this field, gaps remain to be filled. Thus, we expect this review to stimulate research interest towards bridging these gaps, which include the insolubility of some of these macromolecules as well as expanding the scope of the sandwich complexes.

Poly(amido amine)-based mannose-glycodendrimers as multielectron redox probes for improving lectin sensing

An easy-to-prepare series of electroactive poly(amido amine) (PAMAM)-based dendrimers of generations G0 to G2 having mannopyranosylferrocenyl moieties in the periphery to detect carbohydrate-protein interactions is reported. The synthesis involved the functionalization of the PAMAM surface with azidomethylferrocenyl groups and subsequent coupling of mannoside units by the Cu(I)-catalyzed Huisgen reaction. The binding affinity of the series of electroactive glycodendrimers was studied by isothermal titration calorimetry (ITC) and differential pulse voltammetry (DPV). Upon complexation of the glycodendrimers conjugates with prototypical concanavalin A (Con A), voltammograms showed a decrease of the peak current. Such dendrimers showed a notable improvement of redox sensing abilities toward Con A when compared with mono- and divalent analogues, based on both the glycoside multivalent and ferrocene dendritic effects.

Ferrocenyl functionalized silver-chalcogenide nanoclusters

New (chalcogenoethyl)ferrocenylcarboxalate functionalized silver chalcogenide nanoclusters were synthesized using a combination of silylated chalcogen reagents at low temperatures. The addition of E(SiMe(3))(2) to reaction mixtures of FcC{O}OCH(2)CH(2)ESiMe(3) (E = S, Se) and (Ph(3)P)(2)·AgOAc affords nanoclusters with approximate molecular formulas [Ag(36)S(9)(SCH(2)CH(2)O{O}CFc)(18)(PPh(3))(3)] (1), [Ag(100)Se(17)(SeCH(2)CH(2)O{O}CFc)(66)(PPh(3))(10)] (2), and [Ag(180)Se(54)(SeCH(2)CH(2)O{O}CFc)(72)(PPh(3))(14)] (3) as noncrystalline solids. Compositions were formulated on the basis of elemental analysis, high resolution transmission electron microscopy, and dynamic light scattering experiments. Solutions of these polyferrocenyl assemblies display a single quasi-reversible redox wave with some adsorption to the electrode surface as studied by cyclic voltammetry. With the smaller clusters 1, the addition of [Bu(4)N][HSO(4)] results in a shift of the reduction wave to less positive potentials than those of the complex in the absence of these oxoanions. No further shift is observed after the addition of approximately 1 equivalent of HSO(4)(-)/ferrocene branch. Cyclic voltammograms of the larger clusters 2 and 3 show the appearance of a new, irreversible wave at less positive potentials than the initial wave upon the addition of HSO(4)(-). The appearance of this new wave together with the disappearance of the reduction wave indicates a stronger interaction between the nanoclusters and the hydrogen sulfate anion.

Branching the electron-reservoir complex [Fe(eta(5)-C5H5)(eta(6)-C6Me6)][PF6] onto large dendrimers: "click", amide, and ionic bonds

Several strategies have been used to functionalize 1,3,5-trisubstituted arene-cored dendrimers with the organometallic electron-reservoir moiety [Fe(eta(5)-C(5)H(5))(eta(6)-C(6)Me(6))](+), 1, to provide dendritic multielectron reservoirs. They all start from the carboxylic acid [Fe(eta(5)-C(5)H(4)COOH)(eta(6)-C(6)Me(6))][PF(6)], 2, or its acyl chloride derivative [Fe(eta(5)-C(5)H(4)COCl)(eta(6)-C(6)Me(6))][PF(6)], 3. For this purpose, a series of new polyamine dendrimers from G(0) to G(2) with 1--> 3 C connectivity of the branching to the core have been synthesized. Amide, "click" and ionic ammonium carboxylate linkage successfully provided G(0), G(1), and G(2) metallodendrimers with 9, 27, and 81 cationic terminal organoiron groups respectively. Further construction of large metallodendrimers up to G(7) with approximately 14 000 organoiron termini was only possible by combining amide, "click", and tether lengthening strategies to avoid steric bulk at the dendrimer periphery. Reduction of the 18-electron Fe(II) metallodendrimers, exemplified by a G(4)-DAB-64-Fe(II) complex, was achieved exergonically using the parent electron-reservoir complex [Fe(eta(5)-C(5)H(5))(eta(6)-C(6)Me(6))], 1a, at -30 degrees C in MeCN, which allowed further reduction of 64 equiv of C(60) to C(60)(*-) using the 19-electron Fe(I) metallodendrimer.