The diphenyltin(IV) dichloride complex with 1,4-diazcylcoheptane (Homopiperazine) was prepared. Elemental micro-analysis, mass spectral, thermal and spectral measurements were used to reveal the complex structure. The 1:1 complex is formed through coordination of the nitrogen atoms of homopiperaine to Sn. The equilibria involved in the complex formation in solution were investigated. The complexes detected in solutions are of stoichiometric ratio 1:1, including the protonated and hydrolyzed species. The complexes formation constants were estimated using the potentiometric data and the non-linear computer program Miniquad-75. Density Functional Theory (DFT) calculations have been executed to study the equilibrium geometry of homopiperazine and its diphenyltin(IV) complex. The optimization of the diphenyltin(IV) complex structure reveals that the Sn atom is six-coordinate in an octahedral geometry with some distortion where the homopiperazine nitrogen atoms and the two chloride ions are in one plane. The distance between the two nitrogen atoms in the uncomplexed homopiperazine is 3.149 Å and decreased to 2.585 Å in the complex. Bonds connected to N atoms are lengthened upon complex formation. Homopiperazine and its complex were screened against antimicrobial Staphylococcus aureus (+ve), Escherichia coli (-ve) and against antifungal Candida albicans and Aspergillus flavus. Antitumor activities of homopiperazine and its diphenyltin(IV) complexes were tested against breast cancer cell lines. Docking studies confirm the experimental results