<Tr> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> trans - diazene </Td> <Td> cis - diazene </Td> </Tr> <P> In inorganic coordination complexes with octahedral or square planar geometries, there are also cis isomers in which similar ligands are closer together and trans isomers in which they are further apart . </P> <P> For example, there are two isomers of square planar Pt (NH) Cl, as explained by Alfred Werner in 1893 . The cis isomer, whose full name is cis - diamminedichloroplatinum (II), was shown in 1969 by Barnett Rosenberg to have antitumor activity, and is now a chemotherapy drug known by the short name cisplatin . In contrast, the trans isomer (transplatin) has no useful anticancer activity . Each isomer can be synthesized using the trans effect to control which isomer is produced . </P>

Why do cis and trans isomers have different colors