New 1-alkyl-4-(1-alkyl-4-oxo-1,4-dihydroquinolin-2-yl)pyridinium bromides (3a k) were synthesized from 1,4'-diazaflavone [2-pyridin-4-ylquinolin-4(1H)-one] and evaluated for antibacterial and antioxidant activities. A rapid one-pot preparation of 1,4'-diazaflavone (2) was done from 2'-amino substituted chalcone (1) by intramolecular Michael addition using solvent-free microwave heating. New N,N'-dialkyl substituted (C-5-C-15) 1,4'-diazaflavonium bromides were synthesized from compound 2 with corresponding alkyl halides. Compounds 3a k were active against six bacteria (MIC: 7.8-500.0 mu g/mL). They also showed good antioxidant activities in DPPI-1* scavenging (SC50: 45-133 mu g/mL) and ferric reducing/antioxidant power (14-141 p.M TEAC) tests. The biological activities decreased as alkyl chain length increased. The reason behind the obvious negative effect of alkyl chain elongation is unclear and requires investigations about the intermolecular interactions of these pyridinium salts with bioassay components. (C) 2013 Elsevier Masson SAS. All rights reserved.