Synthesis, Characterization, DNA-Binding, and DNA-Photocleavage Properties of [Co(bpy) 2 (7-NO 2 -dppz)] 3+ , [Co(dmb) 2 (7-NO 2 -dppz)] 3+ , and [Co(phen) 2 (7-NO 2 -dppz)] 3+ Complexes: (7-Nitro-dppz = 7-Nitro dipyrido[3,2-a:2′-3′-c]phenazine; bpy = 2,2′-bipyridine; dmb = 4,4′-dimethyl-2,2′-bipyridine; phen = 1,10-phenanthroline) and their Toxicity on Different Microorganisms