Abstract((E)-2-(2-hydroxybenzylideneamino)phenolato-2,2-diphenyl-6-aza-1,3-dioxa-2-stanna- [d,h] dibenzocyclononene, [Sn(Ph 2 SB)] (compound 1, where Ph 2 SB=(E)-2-(2-hydroxybenzylideneamino)phenolato Schiff base) and two novel compounds, [[SnPh 2 (F-azoSB)] (compound 2, where F-azoSB=4-((E)-(4-fluorophenyl) diazenyl)-2-((E)-(2-hydroxyphenylimino)methyl)phenolato Schiff base), [[SnPh 2 (sulf-azoSB)]0.125CHCl 3 (compound 3, where sulfamerazineazosalSB=4-((E)-(4-hydroxy-3-((E)-(2-hydroxyphenylimino)methyl)phenyl)diazenyl)-N-(4-methylpyrimidin-2-yl) benzenesulfonamide Schiff base), and the control compound, cisplatin (compound 4) were analysed to comparatively determine their effect on cancer cell growth. Anti-cancer properties of compounds 1-4 were examined using glioblastoma (U-1242 MG), colorectal (HT-29 and HCT-116), and skin (A431) human cancer cell lines. With regards to human glioblastoma cells, compounds 1 and 3 demonstrated anti-proliferative capacity in the cell line tested. Specifically, compounds 1 and 3 inhibited cell proliferation by 50% at concentrations between 10 and 50 µM. With respect to colon cancer cell lines, the IC 50 values for compounds 1-3 ranged from 3.04 ± 0.98 to 104.51 ± 13.87 µM. In the case of HCT-116, this translates to a 3-to 73-fold inhibitory effect of compounds 1-3 over cisplatin. In all cell lines tested, the chemo-effect was more pronounced with compounds 1-3 than with the control (compound 4); demonstrating that these azo-containing Sn(IV) complexes were more potent than compound 4. The overall effect of compounds 1-3 in the induction of appotosis and the inhibition of proliferation have defined an essential role for these compounds in chemotherapy. IntroductionFrom the late 1960s until the present, there have been significant advances in both the early detection and the treatments of cancer. Despite these advances overall incidences of cancer and deaths from cancer have increased during the same period [1]. These counterintuitive increases have been the impetus for development of new drugs for cancer treatment. In this context the organometallic compounds have been widely investigated as potential anti-tumour agents. Metallocene dihalide complexes Cp 2 MX 2 (where M=titanium, vanadium, niobium, or molybdenum) were the first early transition metal complexes that were shown to have anti-tumour activity. In addition, the organometallic-DNA and organometallic-nucleic acid interactions of these compounds have also been investigated [2][3][4]. More recently, ferricenium salts, organotin, and bismuth complexes have also emerged as examples of organometallic compounds that have been found to exhibit interesting anti-tumour activity [5].The biological activity of organotin compounds has become well known due to their practical applications as fungicides, bactericides, biocides, and pesticides [3,[6][7][8]. It is now well established that organotin compounds are very important in cancer chemotherapy [9] and as potential anti-cancer agents [10][11][12][13]. This is due in part to thei...