The N/N donor-type bromobenzyldiamines (1-3) were successively prepared by reduction of Schiff bases formed as a result of condensation reactions of 4-bromobenzaldehyde with aliphatic diamines. The Cl exchange reactions of hexachlorocyclotriphosphazene (HCCP; trimer; N3P3Cl6; 4) with the bidentate ligands (1-3) produced the new monospiro- (5-7) and dispirocyclotriphosphazenes (8-13) containing 4-bromo-benzyl pendant arm(s). The tetrachloro phosphazenes (5-7) were reacted with pyrrolidine, tetra-1,4-dioxa-8-azaspiro [4.5]decane (DASD) and piperidine to give the tetraamino substituted mono-spirophosphazenes (5a-7c). The spectral analyses of all the phosphazenes were made using appropriate spectroscopic methods; such as FTIR, H-1, C-13, P-31 NMR and ESI-MS. The molecular and crystal structures of 5, 6, 7 and 12 were also determined by X-ray crystallography. On the other hand, the antimicrobial activities of the phosphazenes were evaluated against G (-) and G (+) bacteria and fungi. Some of the tetraaminophosphazenes were found to be very active against several bacteria and fungi. Besides, the interactions of the cyclotriphosphazenes with plasmid DNA were investigated using agarose gel electrophoresis. (C) 2020 Elsevier B.V. All rights reserved.