Patent ID: 8598575

Claim:
A compound having formula I: wherein: W 1 and W 2 independently are —(CR c R d ) m — or —(SiR e R f )—; X and X′ are selected from the group consisting of S, O, NR a and CR b , provided that one of X and X′ is selected from the group consisting of S, O, and NR a , and the other X and X′ is CR b ; Y and Y′ are selected from the group consisting of S, O, NR a′ and CR b′ , provided that one of Y and Y′ is selected from the group consisting of S, O, and NR a′ , and the other Y and Y′ is CR b′ ; Z 1 and Z 2 independently are selected from the group consisting of O, S, —C≡C—, and a covalent bond; R a and R a ′ independently are selected from the group consisting of H, a C 1-20 alkyl group, a C 2-20 alkenyl group, and a C 1-20 haloalkyl group; R b and R b ′ independently are selected from the group consisting of H, a C 1-20 alkyl group, a C 2-20 alkenyl group, and a C 1-20 haloalkyl group; R c and R d independently are selected from the group consisting of H, a C 1-20 alkyl group, and a C 1-20 haloalkyl group; R e and R f independently are selected from the group consisting of H, a C 1-20 alkyl group, and a C 1-20 haloalkyl group; R 1 , R 1 ′, R 2 , and R 2 ′ independently are selected from the group consisting of a linear C 1-40 alkyl group, a linear C 2-40 alkenyl group, and a linear C 1-40 haloalkyl group; and m, at each occurrence, independently is 0, 1, 2, 3, or 4.