To investigate the influence of the cyano groups on the thiophene rings introduced for the stabilization of isophlorin 1c, we calculated the structure of derivative 1f without cyano groups. The mpd of 1f was 0.294, indicating higher planarity (lower mpd) than 1c. Additionally, the tilt angle of the substituents was larger (57.6°) than that of 1c. These results demonstrate that the cyano groups on the thiophene rings significantly affect the structure of the isophlorin ring.