**Corentin Pigot 1,\*, Guillaume Noirbent 1,\*, Thanh-Tuân Bui 2, Sébastien Péralta 2, Didier Gigmes 1, Malek Nechab <sup>1</sup> and Frédéric Dumur 1,\***


Received: 5 April 2019; Accepted: 22 April 2019; Published: 24 April 2019

**Abstract:** A series of ten push-pull chromophores comprising 1*H*-cyclopenta[*b*]naphthalene-1,3(2*H*)-dione as the electron-withdrawing group have been designed, synthesized, and characterized by UV-visible absorption and fluorescence spectroscopy, cyclic voltammetry and theoretical calculations. The solvatochromic behavior of the different dyes has been examined in 23 solvents and a positive solvatochromism has been found for all dyes using the Kamlet-Taft solvatochromic relationship, demonstrating the polar form to be stabilized in polar solvents. To establish the interest of this polyaromatic electron acceptor only synthesizable in a multistep procedure, a comparison with the analog series based on the benchmark indane-1,3-dione (1*H*-indene-1,3(2*H*)-dione) has been done. A significant red-shift of the intramolecular charge transfer band has been found for all dyes, at a comparable electron-donating group. Parallel to the examination of the photophysical properties of the different chromophores, a major improvement of the synthetic procedure giving access to 1*H*-cyclopenta[*b*]naphthalene-1,3(2*H*)-dione has been achieved.

**Keywords:** push-pull dyes; chromophore; naphthalene; solvatochromism
