Aryl substituted adamantane–dipyrromethanes: chromogenic and fluorescent anion sensors

New adamantane–dipyrromethane anion receptors were synthesized and their photophysical properties and anion binding investigated. In addition, a nitro derivative has been characterized by single crystal X-ray analysis. In the crystal structure, the nitro derivative is complexed with CH3CN molecules, indicating that dipyrromethanes can in principle be employed as neutral molecule hosts. Anion binding ability in CH3CN solutions with TBA salts (F−, Cl−, Br−, AcO−, HSO4−, NO3− and H2PO4−) was investigated by UV–vis, fluorescence and/or 1H NMR spectroscopy, and the association constants of the corresponding complexes were determined. The receptors form 1:1 complexes with the highest association constants with F− and AcO−. Change of the substituent at the phenyldipyrromethanes results in different photophysical properties, leading to different spectroscopic responses in the presence of anions. Therefore, differently substituted phenyldipyrromethanes can be used as colorimetric or fluorescent anion sensors.

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