Rhenium tricarbonyl complexes of AIE active tetraarylethylene ligands: tuning luminescence properties and HSA-specific binding

Abstract

The synthesis and photophysical properties of luminescent Re(i) tricarbonyl complexes prepared from bis(pyridyl)- and bis(quinolyl) tetraarylethylene (TAE) ligands are reported. Emission wavelengths of the complexes are influenced by structural variation in the tetraarylethylene ligands, and several complexes display aggregation-induced enhanced emission in aqueous solution. A Re(i) complex prepared from an indole-functionalized TAE ligand shows significant enhancement in its luminescence intensity accompanied by a remarkable blue shift (∼95 nm) upon specific binding to site II of human serum albumin.

Rhenium Complexes of Bis(benzothiazole)‐Based Tetraarylethylenes as Selective Luminescent Probes for Amyloid Fibrils

“…The synthesis of TAE ligands employed in this study is shown in Scheme . The route used to construct ligands 6 – 8 is analogous to procedures we have previously reported for the preparation of related TAE derivatives . Briefly, dibromoalkene 5 was obtained upon treatment of bis(benzothiazol‐2‐yl)methanone ( 4 ) with CBr 4 and PPh 3 .…”

“…The route used to construct ligands 6-8 is analogous to procedures we have previously reported for the preparation of related TAEd erivatives. [4] Briefly,d ibromoalkene 5 was obtained upon treatment of bis(benzothiazol-2-yl)methanone (4)w ith CBr 4 and PPh 3 .S ubsequent double Suzuki reaction of 5w ith aryl boronic acids or pinacol esters then afforded 6-8 in good yields.…”

“…For example, incorporation of 5-indolyl groups as non-coordinating arenesi nabis(quinolyl)Re I complex affordedaturn-onl uminescent bioprobe for selectivem onitoring of human serum albumin( HSA). [4] In this work we demonstrate the versatilityo ft his bioprobe designs trategy through construction of TAE-Re I complexes for targeted luminescentd etection of amyloid fibrils. Certain intrinsically unfolded or misfolded small peptides are known to undergoa ggregation throughf ormationo fb-sheet structures, leadingt oi nsoluble protein deposits known as amyloid fibrils.…”

“…This allows the non‐coordinating arene groups to be used for tuning photophysical properties (e.g., absorption and emission wavelength) and as biomolecular targeting moieties for selective bioimaging applications. For example, incorporation of 5‐indolyl groups as non‐coordinating arenes in a bis(quinolyl)Re I complex afforded a turn‐on luminescent bioprobe for selective monitoring of human serum albumin (HSA) …”

“…[3] We recently reported the design and synthesis of new Re I (CO) 3 complexes that feature chelatingb is(pyridyl) or bis-(quinolyl) ligands derived from tetraarylethylene( TAE) scaffolds (Figure 1). [4] While the TAEl igands themselves possess fluorescent properties that emerge upon rigidification of the tetraarylethylene framework (i.e.,a ggregation-induced emission or AIE), [5] we envisioned introduction of the fac-Re(CO) 3 fragment wouldo pen new emissive channels via contributionsf rom 3 MLCT exciteds tates. This allows the non-coordinating arene groups to be used for tuning photophysical properties (e.g., absorption and emission wavelength)a nd as biomolecular targetingm oietiesf or selectiveb ioimaging applications.…”