Mohamed El-Sayed

The Solvent-Like Nature of Silica Particles in Organic Solvents

Kamlet-Taft’s α (hydrogen bond donor acidity) and π* (dipolarity/polarizability) values of various silica batches measured in various solvents are presented. The α and π* parameters for the various solid acids are analyzed by means of Fe(phen)2(CN)2 (cis-dicyano-bis-(1,10)-phenanthroline-iron(II), 1), Michler’s ketone (4,4′-bis-(dimethylamino)-benzophenone, 2), and two hydrophilic derivatives of 2, (4-(dimethylamino)-4′-(di-2-hydroxyethyl)-amino-benzophenone (3a) and 4,4′-bis-(di-(2-hydroxyethyl)-amino)-benzophenone (3b) as well as coumarin 153 (4) as solvatochromic surface polarity indicators. Apparent β (hydrogen bond acceptor basicity) parameters for bare silica have been evaluated by means of an aminobenzodifuranone dye (5) as solvatochromic probe.