The electronic, optical and magnetic consequences of delocalization in multifunctional donor-acceptor organic polymers

Two organic polymers containing alternating electron donating triarylamine and electron accepting thiazolo[5,4-d]thiazole (TzTz) moieties have been synthesized and their redox states investigated. When donor and acceptor units are proximal (polymer 1), electron density is delocalized, leading to a small electrical and optical band gap; these are larger with the inclusion of an adjoining alkynyl-phenyl bridge (polymer 2), where electron density is more localized due to the rotation of the monomer units. As a result, 1 and 2 display different optical and fluorescence properties in their neutral states. Upon chemical and electrochemical redox reactions, radicals form in both 1 and 2, yielding magnetic materials that display temperature independent paramagnetism, attributable to delocalization of radical spins along the polymeric backbones. The ability to convert between diamagnetic and paramagnetic states upon chemical oxidation and/or reduction allows for the materials to display switchable magnetism and fluorescence, imparting multifunctionality to these solid-state purely organic materials.

Research Highlight Nanomedicine: MOFs deliver
Nature Chemistry 7, 270–271 (2015) doi:10.1038/nchem.2229
Published online 

As of January 2015, I have taken up a position based in the London office of Nature Publishing Group. I will be working as an assistant editor at Nature Communications.

Nature Communications is an open access journal that publishes high-quality research from all areas of the natural sciences and has an Impact Factor of 10.742 according to the 2013 Journal Citation Reports® Science Edition (Thomson Reuters, 2014). Papers published by the journal represent important advances of significance to specialists within each field.




Experimental and Computational Studies of a Multi-Electron Donor–Acceptor Ligand Containing the Thiazolo[5,4-d]thiazole Core and its Incorporation into a Metal–Organic Framework

A ligand containing the thiazolo[5,4-d]thiazole (TzTz) core (acceptor) with terminal triarylamine moieties (donors), N,N′-(thiazolo[5,4-d]thiazole-2,5-diylbis(4,1-phenylene))bis(N-(pyridine-4-yl)pyridin-4-amine (1), was designed as a donor–acceptor system for incorporation into electronically active metal–organic frameworks (MOFs). The capacity for the ligand to undergo multiple sequential oxidation and reduction processes was examined using UV/Vis-near-infrared spectroelectrochemistry (UV/Vis-NIR SEC) in combination with DFT calculations. The delocalized nature of the highest occupied molecular orbital (HOMO) was found to inhibit charge-transfer interactions between the terminal triarylamine moieties upon oxidation, whereas radical species localized on the TzTz core were formed upon reduction. Conversion of 1 to diamagnetic 2+ and 4+ species resulted in marked changes in the emission spectra. Incorporation of this highly delocalized multi-electron donor–acceptor ligand into a new two-dimensional MOF, [Zn(NO3)2(1)] (2), resulted in an inhibition of the oxidation processes, but retention of the reduction capability of 1. Changes in the electrochemistry of 1 upon integration into 2 are broadly consistent with the geometric and electronic constraints enforced by ligation.

I will be attending the 4th International Conference on Metal-Organic Frameworks and Open Framework Compounds in Kobe, Japan from 28th September – 2nd October 2014. For more information please visit the dedicated page here.

It took a while but here’s my latest work including some pretty nice interpenetration isomers!

The metalloligand [Ni(pedt)2]- (pedt = 1-(pyridine-4-yl)ethylene-1,2-dithiolate) has been incorporated into two multi-dimensional structures for the first time. These coordination frameworks represent highly unusual interpenetration isomers and exhibit solid state redox and optical properties that reflect the electronically delocalised nature of the metalloligand.

Chanel Leong’s beautiful work has just been published in Chemical Science!

The presence of donor–acceptor charge transfer in a tetrathiafulvalenenaphthalene diimide-based metal–organic framework (MOF) is investigated using a complementary suite of solid state spectroscopic and electrochemical techniques, and is supported by computational calculations. Solid state electron paramagnetic resonance (EPR) spectroelectrochemistry was employed as a novel method for charge transfer characterization in MOFs.

I am delighted to have been informed today by the international committee from the European Institute of Molecular Magnetism that I have been awarded the