Synthesis and anion binding properties of 2,5-diamidothiophene polypyrrole Schiff base macrocycles

[reaction: see text] Two easy-to-synthesize polypyrrolic 2,5-diamidothiophene Schiff base macrocycles are reported, along with their anion binding properties as determined via UV-vis spectroscopic titrations carried out in dichloroethane. There is a striking difference between the interactions with anions of the two macrocycles, a finding ascribed to differences in their rigidity. For example, the more flexible dipyrromethane-derived macrocycle displays a 1.2:1 hydrogen sulfate versus nitrate selectivity, while its more rigid bipyrrole-derived congener shows a 7.4:1 selectivity in favor to hydrogen sulfate.     

Mono- and Diamination of 4,6-Dichloropyrimidine, 2,6-Dichloropyrazine and 1,3-Dichloroisoquinoline with Adamantane-Containing Amines

N-heteroaryl substituted adamantane-containing amines are of substantial interest for their perspective antiviral and psychotherapeutic activities. Chlorine atom at alpha-position of N-heterocycles has been substituted by the amino group using convenient nucleophilic substitution reactions with a series of adamantylalkylamines. The prototropic equilibrium in these compounds was studied using NMR spectroscopy. The introduction of the second amino substituent in 4-amino-6-chloropyrimidine, 2-amino-chloropyrazine, and 1-amino-3-chloroisoquinoline was achieved using Pd(0) catalysis.     

Electrochemical synthesis of a thiophene-containing cyclo[9]pyrrole

A new member of the cyclo[n]pyrrole class of expanded porphyrins could be prepared from the corresponding thiophene-containing terpyrrole precursor through use of a mild electrochemical oxidative procedure. The isolated macrocycle, featuring nine heterocyclic subunits directly connected through their α,α'-positions, is the largest cyclo[n]pyrrole derivative reported to date (see figure).     

Cyclo[m]pyridine[n]pyrroles: hybrid macrocycles that display expanded π-conjugation upon protonation

Novel hybrid cyclo[m]pyridine[n]pyrroles have been synthesized using Suzuki coupling. Their NMR and optical spectroscopic features and solid state structural parameters provide support for the proposal that these species are best described as locally aromatic compounds devoid of long-range intersubunit conjugation. However, an extension of the π-conjugation in the macrocycles can be realized through protonation, as inferred from optical spectroscopic and X-ray diffraction-based structural studies.     

π-Extension in expanded porphyrins: cyclo[4]naphthobipyrrole

The π-extended cyclo[4]naphthobipyrrole 1a has been prepared via an Fe(III)-mediated oxidative cyclization of an alkyl-substituted naphthobipyrrole. The structure of this new expanded porphyrin, isolated as the deprotonated sulfate salt, was characterized by spectroscopic means, as well through a single crystal X-ray diffraction analysis. Salt 1a displays a total of four well-resolved redox waves as determined by cyclic voltammetry. It also displays bathochromically shifted near-IR absorption maxima compared to the diprotonated forms of nonannulated cyclo[8]pyrroles.     

Naphthobipyrrole: versatile synthesis and electropolymerization

A facile synthetic route to a new polycyclic pyrrole derivative, 3,8-diethyl-1,10-dihydro-benzo[e]pyrrolo[3,2-g]indole (1), is reported. This annulated bipyrrole acts as a monomer for electropolymerization and forms an electrochromic conducting polymer (poly1) when electrooxidized at low potentials (0.4 V vs Ag/Ag(+)) in acetonitrile. The presence of alkyl substituents at the 3 and 8 carbons (β-pyrrolic positions) induces regioselective 2,5'-coupling of the pyrrole repeat units and gives rise to the more uniform polymeric product, poly1. Poly1 exhibits globular morphology, as judged from SEM pictures. Its spectroelectrochemical features can be attributed to the formation of four possible states: neutral, polaron, bipolaron, and transverse bipolaron. The relatively low switching potentials (-0.6 to +0.9 V vs Ag/Ag(+) in MeCN) displayed by poly1 leads us to suggest that 1 has a role to play as a polymerizable moiety for the development of multicolor electrochromic materials.     

Photodriven Charge Separation and Transport in Self‐Assembled Zinc Tetrabenzotetraphenylporphyrin and Perylenediimide Charge Conduits

Zinc tetrabenzotetraphenyl porphyrin (ZnTBTPP) covalently attached to four perylenediimide (PDI) acceptors self‐assembles into a π‐stacked, segregated columnar structure, as indicated by small‐ and wide‐angle X‐ray scattering. Photoexcitation of ZnTBTPP rapidly produces a long‐lived electron–hole pair having a 26 Å average separation distance, which is much longer than if the pair is confined within the covalent monomer. This implies that the charges are mobile within their respective segregated ZnTBTPP and PDI charge conduits.