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The design of bright, high quantum yield (QY) materials in the near‐infrared (NIR) spectral region in water remains a significant challenge. A series of cyanine and squaraine dyes varying water solubilizing groups and heterocycles are studied to probe the interactions of these groups with albumin in water. Unprecedented, ′ultra‐bright′ emission in water is observed for a sulfonate indolizine squaraine dye (61.1 % QY) and a sulfonate indolizine cyanine dye (46.7 % QY) at NIR wavelengths of >700 nm and >800 nm, respectively. The dyes presented herein have a lower limit of detection than the most sensitive dyes known in the NIR region for albumin detection by at least an order of magnitude, which enables more sensitive diagnostic testing. Additionally, biotinylated human serum albumin complexed with the dyes reported herein was observed to function as an immunohistochemical reagent enabling high resolution imaging of cellular α‐tubulin at low dye concentrations.

The ever‐expanding need for renewable energy can be addressed in part by photocatalytic CO₂reduction to give fuels via an artificial photosynthetic process driven by sunlight. A series of rhenium photocatalysts are evaluated in the photocatalytic CO₂reduction reaction and via photophysical, electrochemical, and computational studies. The impact of various electron withdrawing substituents on the aryl group of the pyNHC‐aryl ligand along with the impact of extending conjugation along the backbone of the ligand is analyzed. A strong correlation between excited‐state lifetimes, photocatalytic rates, and computationally determined dissociation energy of the labile ligand of these complexes is observed. Additionally, computed orbital analysis provides an added understanding, which allows for prediction of the potential impact of an electron withdrawing substituent on photocatalysis.