A coordination polymer (SCP), [Cu2(CN)4·(Me3Sn)2·(phen)2], 1, was constructed based on phenanthroline monohydrated (phen), trimethyltin chloride, and K3[Cu(CN)4]. The SCP 1 consists of repeating units of tetrahedral Cu(N2C2) fragments connected by (Me3Sn)+ cations which create 1-D helical chains with the phen ligands arranged on both sides of the chain. The 1-D helical chains are arranged in a unique way to form two right-helical and two left-helical chains creating a rare quartet-helical 3-D network. The quartet-helical chains are arranged in a unique A⋯A⋯A fashion forming a 3-D network structure via H-bonds and π–π stacking. Mass, electronic and luminescence spectra are also investigated. The MTT assay was used to determine the in vitro antitumor effects of SCP 1 on human breast cancer cell line, MCF-7. Cell cycle analysis revealed that SCP 1 induced apoptosis in MCF-7 breast cancer cell line. Thus, the SCP 1 selectivity exhibits specific in vitro antitumor effects against human breast cancer cell line,...