compounds of the general formula : ## str1 ## wherein r 1 is an isomer of phthalaldehyde ; r 2 is an isomer of anromatic dialdehyde selected from the class consisting of phthalaldehyde , naphthalene dialdehyde , phenanthrene dialdehyde , anthracene dialdehyde , biphenyl dialdehyde , terphenyl dialdehyde ; and mixtures thereof and r 3 is an isomer of an aromatic diamine selected from the class consisting of benzene diamine , naphthalene diamine , phenanthrene diamine , biphenyl diamine , and terphenyl diamine , and the cyano - condensation resins thereof which are useful in preparing semiconductors .