Most anions are too hydrophilic to spontaneously migrate through lipid bilayers. At the same time, however, their transport is necessary for life. For example, cellular respiration – a complex biochemical process through which every living cell produces energy – involves the facilitated transport of chloride, bicarbonate as well as various carboxylates and phosphates across lipid bilayers. In cells, this is usually accomplished by specialised proteins, and hence their dysfunction can cause serious diseases. Accordingly, the development of artificial anion transporters (anionophores) is currently a “hot topic” in supramolecular chemistry.

Fig. 1. Anion transport through lipid bilayers of synthetic liposomes facilitated by synthetic transporters

Surprisingly however, most of the previous studies in this field were focused on chloride transporters, even though in Nature the transport of other anions also plays a significant role. This is most probably due to the lack of direct and convenient methods to follow the transport of other anions. Our new project aims to develop new, direct methods of measuring anion transport for a broad range of biologically important anions and to use these methods to develop selective artificial anion transporters. One particularly ambitious goal of this project is to develop enantioselective anion transporters, an achievement which has no precedents in literature thus far.

Small molecules able to selectively transport biologically relevant anions, such as basic forms of amino acids, nucleotides, metabolites or drugs, may have interesting biological activity and may find applications in medicine, sensor technology and separation of mixtures, including the mixtures of enantiomers.

Currently, we are looking for prospective MSc and PhD students as well as postdoctoral researchers willing to join the project. We offer state-of-the-art research facilities and attractive fellowships! For more details, contact me via e-mail: mchmielewski@chem.uw.edu.pl or follow the News section on the main page.

PhD and MSc positions are available within ‘OPUS’ grant from the Polish National Science Centre. The aim of the project is to create a revolutionary new class of ‘intelligent’ MOFs, able to adapt to their environment in response to external physical or chemical stimuli (see the scheme below).

How to kill two binding sites with one photoswitch? Check it out in our newest communication in JACS!

Simple and easy to make diamidocarbazoles have been shown to be highly active anion transporters through lipid bilayers and sensitive turn-ON fluorescent sensors for H₂PO₄^– and AcO^–. See our newest paper in OBC:

Metal-organic frameworks (MOFs) decorated with stable organic radicals are highly promising materials for redox catalysis. Unfortunately however, the synthesis of chemically robust MOFs typically requires harsh solvothermal conditions, which are not compatible with organic radicals. Here we describe the synthesis of two isoreticular families of stable, mixed-component, zirconium MOFs with UiO-66 and UiO-67 structure and controlled amounts of covalently attached TEMPO radicals. The materials were obtained using a relatively low-temperature, HCl-modulated de novo method developed by Hupp and Farha and shown to contain large amounts of missing cluster defects, forming nanodomains of reo phase with 8-connected clusters. In the extreme case of homoleptic UiO-67-TEMPO(100%), the material exists as an almost pure reo phase. Large voids due to missing clusters and linkers allowed these materials to accommodate up to 2 times more of bulky TEMPO substituents than theoretically predicted for the idealized structures and proved to be beneficial for catalytic activity. The TEMPO-appended MOFs were shown to be highly active and recyclable catalysts for selective aerobic oxidation of a broad range of primary and secondary alcohols under exceptionally mild conditions (RT, atmospheric pressure of air). The influence of various parameters, including pore size and TEMPO content, on the catalytic activity was also comprehensively investigated.

A versatile method for the post-synthetic removal of primary amino groups from metal-organic frameworks (MOFs) has been developed. The method allowed the first successful synthesis of the missing parent compound of an important family of MOFs – the unsubstituted (Al)MIL-101. The material was shown to be a useful reference compound for the elucidation of the role of amino groups in the adsorption and deactivation of olefin metathesis catalysts. The chemoselectivity of the deamination is sufficient for the selective removal of NH₂ substituents from mixed-linker MOFs bearing both NH₂ and RCONH groups.

Joining together two diamidocarbazole moieties with a flexible linker led to a selective fluorescent sensor for an extremely hydrophilic sulfate anion, which works even in the presence of 25% of water! It allowed sulfate detection in real world samples, such as mineral waters, which contain many other anions. See more.

Diaminocarbazole was also used to construct a new catalytic system, composed of bimetallic Au@Pt nanoparticles dispersed in a conducting polymer. Our new organic-inorganic hybrid system shows enhanced activity towards formic acid electrooxidation. See more.