ORIGINAL ARTICLE Synthesis and Spectroscopic Studies of N,N’-dialkyl Derivatives of Antisymmetrical 2H,5H-Dihydropyrrolo [3,4-c]pyrrole-1,4-diones Secil Celik Erbas & Serap Alp Received: 27 May 2013 /Accepted: 21 August 2013 /Published online: 19 September 2013 # Springer Science+Business Media New York 2013 Abstract 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione deriva- tives (DPP) are chemically stable, fluorescent molecules, known as High Performance Pigments. Preparation of the soluble derivatives of DPPs provides great advantage in de- signing the optic sensor for new and existing applications and overcoming aggregation problems in solid matrices. For this purpose, the synthesis of antisymmetric DPPs and the forma- tion of new organic dyes through N,N’-dialkylation and their spectroscopic studies have been carried out both in solutions and in solid phase. Keywords High performance pigments . Fluorophores . Antisymmetric . Diketopyrrolopyrrole Introduction Diketopyrrolopyrrole derivatives (DPPs) have been used in plas- tic coloring, surface coatings, and as colour filters due to their luminous colours as well as high stability. Today they are widely used in many optic systems, such as information storage and monitoring devices. In most of the recent studies, the usages of DPPs in optic systems have been taken into consideration. For example Fukuda et al., have developed a thin film ring laser system using DPP derivatives. DPPs have also been used as organic semiconductors for organic solar cell applications and have been converted a ‘latent ’ pigment [1–13]. When the literature on DPPs is scrutinized, it becomes clear that the spectroscopic characteristics of DPPs are related to the 3,6-diaryl moieties. The effect of electron-donor and electron- acceptor groups on the aryl moieties has been investigated through maximum absorption wavelengths [14]. In this study, six new antisymmetrical DPP derivatives have been synthesized by base catalyzed condensation reactions using aromatic nitriles and pyrrolinone esters. Furthermore, structural analysis, photophysical characteristics and photostabilities of the newly prepared DPPs in different media are reported. Thus, antisymmetric 3-phenyl,6-pyridyl-2,5-dimethyl- pyrrolo[3,4-c]pyrrole-1,4-dione (DPP-1a), Diethyl-2,2’-(1,4- dioxo-3-phenyl-6-pyridine-4-yl-pyrrolo[3,4-c]pyrrole-2,5- diyl)diacetate (DPP-1b), 3-tolyl,6-pyridyl-2,5-dimethyl- pyrrolo[3,4-c]pyrrole-1,4-dione (DPP-2a), Diethyl-2,2’-[1,4- dioxo-3-(4-methylphenyl)-6-pyridine-4-yl-pyrrolo[3,4-c]pyr- role-2,5-diyl)diacetate (DPP-2b), 3-methoxyphenyl,6-phenyl- 2,5-dimethylpyrrolo[3,4-c]pyrrole-1,4-dione (DPP-3a) and Diethyl-2,2 ’ -[1,4-dioxo-3-(4-p-methoxyphenyl)-6- phenylpyrrolo[3,4-c]pyrrole-2,5-diyl)diacetate (DPP-3b) de- rivatives have been synthesized and their structural identifica- tions have been made using FT-IR, NMR and LC-MS spectra. To determine the photophysical characteristics of the six new- ly synthesized DPPs, UV–vis absorption and emission spec- troscopy techniques have been used. The maximum absorp- tion and emission wavelengths, molar extinction coefficients (ε), singlet energy levels (Es), Stokes’ shift values (Δλ) and quantum yields (φ F ) of DPPs are given. In addition, the photostabilities of all derivatives have been investigated in solutions of dimethylformamide (DMF), acetonitrile (ACN), chloroform (CHCl 3 ), tetrahydrofuran (THF), toluene and in a solid matrix of PVC. Figure 1 shows schematic structures of the six different synthesized antisymmetrical N,N’-dialkyl DPP derivatives. S. C. Erbas : S. Alp Department of Chemistry, University of Dokuz Eylul, The Graduate School of Natural and Applied Sciences, 35160 Izmir, Turkey S. C. Erbas e-mail: secil.celik@cbu.edu.tr S. Alp (*) Department of Chemistry, University of Dokuz Eylul, Faculty of Sciences, 35160 Izmir, Tinaztepe, Turkey e-mail: serap.alp@deu.edu.tr J Fluoresc (2014) 24:329–335 DOI 10.1007/s10895-013-1294-7