Organic compounds of formula I may be used in optoelectronic devices wherein R1 is, independently at each occurrence, a C1-C20 aliphatic radical, a C3-C20 aromatic radical, or a C3-C20 cycloaliphatic radical; R2 is, independently at each occurrence, a C1-C20 aliphatic radical, a C3-C20 aromatic radical, or a C3-C20 cycloaliphatic radical; a is, independently at each occurrence, an integer ranging from 0-4; b is, independently at each occurrence, an integer ranging from 0-3; Ar1 is a direct bond or heteroaryl, aryl, or alkyl or cycloalkyl; Ar2 is heteroaryl, aryl, or alkyl or cycloalkyl; c is 0, 1 or 2; and n is an integer ranging from 2-4.