porphyrins

Global aromaticity at the nanoscale

Does aromaticity have a size limit? Evidence is presented for global aromaticity in porphyrin nanorings with circuits of up to 162 π-electrons. The conformation of the nanoring can be altered by changing the template, which in turn controls the …

Mechanisms of IR amplification in radical cation polarons

Break down of the Born–Oppenheimer approximation is caused by mixing of electronic and vibrational transitions in the radical cations of some conjugated polymers, resulting in unusually intense vibrational bands known as infrared active vibrations …

Time-Resolved Structural Dynamics of Extended π-Electron Porphyrin Nanoring

The design of molecular structures inspired by naturally occuring light harvesting systems has been intensely pursued over the last couple of decades. Interesting new structures include the π-conjugated porphyrin nanorings, which show promising …

Probing the orientation of porphyrin oligomers in a liquid crystal solvent – a triplet state electron paramagnetic resonance study

Linear porphyrin oligomers have found various applications as synthetic molecular wires in the context of light harvesting, solar energy conversion and molecular electronics. In many of these applications a partial ordering of the molecules helps to …

Aromaticity and Antiaromaticity in the Excited States of Porphyrin Nanorings

Aromaticity can be a useful concept for predicting the behavior of excited states. Here we show that π-conjugated porphyrin nanorings exhibit size-dependent excited-state global aromaticity and antiaromaticity for rings containing up to eight …

Global Aromaticity and Antiaromaticity in Porphyrin Nanoring Anions

Doping, through oxidation or reduction, is often used to modify the properties of π-conjugated oligomers. In most cases, the resulting charge distribution is difficult to determine. If the oligomer is cyclic and doping establishes global aromaticity …

Band Structures of Periodic Porphyrin Nanostructures

Recent progress in the synthesis of π-conjugated porphyrin arrays of different shapes and dimensionalities motivates us to examine the band structures of infinite (periodic) porphyrin nanostructures. We use screened hybrid density functional theory …

Template-Directed Synthesis of a Conjugated Zinc Porphyrin Nanoball

We report the template-directed synthesis of a π-conjugated 14-porphyrin nanoball. This structure consists of two intersecting nanorings containing six and 10 porphyrin units. Fluorescence upconversion spectroscopy experiments demonstrate that …

Detection of a weak ring current in a nonaromatic porphyrin nanoring using magnetic circular dichroism

We compare the absorption and magnetic circular dichroism (MCD) spectra of a series of porphyrin oligomers – dimer, tetramer, and hexamer – bound in a linear or cyclic fashion. The MCD signal is extremely weak for low energy transitions in the linear …

Electronic Delocalization in the Radical Cations of Porphyrin Oligomer Molecular Wires

The radical cations of a family of π-conjugated porphyrin arrays have been investigated: linear chains of N = 1–6 porphyrins, a 6-porphyrin nanoring and a 12-porphyrin nanotube. The radical cations were generated in solution by chemical and …