Organic–inorganic hybrids (OIH) are materials that can be easily synthesized by the sol–gel method and combine the advantages of organic and inorganic moieties within a single polymeric matrix. Imidazole derivatives are versatile organic compounds that can change their optical properties with the variation of pH due to the protonation or deprotonation of the nitrogen atoms. This work reports the preparation of different OIHs doped with different contents of two imidazole compounds (3a,b). The obtained materials were characterized structurally by FTIR, and the dielectric properties were studied by electrochemical impedance spectroscopy. The optical properties were studied by UV-Vis absorption and fluorescence spectroscopies. The FTIR analysis showed that the presence of the imidazole does not change the structural properties of the matrices. The normalized resistance values obtained for the doped matrices ranged between 8.57 and 9.32 Ω cm², all being higher than the undoped matrix. The σ ranged between 9.49 and 10.28 S cm⁻¹, being all higher than the pure OIH samples. Compound 3a showed a maximum absorption peak at 390 nm, which is present in the OIH spectra, proving the presence of the compound. In the case of compound 3b, a maximum absorption wavelength at 412 nm was found, and the compound peak was not clear, which may indicate that an interaction between the compound and the matrix occurred. A synergetic effect between the intrinsic emission of the matrix and the fluorescence of 3a is found on the OIH-doped matrices.

Two novel dicyanovinyl derivatives 3a–b were synthesized in moderate to good yields through a Knoevenagel reaction of the corresponding aldehyde precursors and malononitrile. The photophysical properties of the new push-pull systems were studied by UV-vis and fluorescence spectroscopy in acetonitrile. The evaluation of the compounds as colorimetric chemosensors was carried out by performing spectrophotometric titrations in acetonitrile and acetonitrile/water in the presence of relevant organic and inorganic anions, and of alkaline, alkaline-earth and transition metal cations. The benzoindole derivative exhibited great selectivity for the cyanide anion over other anions in acetonitrile/water (8:2) solution showing a distinct color change from colorless to yellow.

In recent years the research of sensors with good sensitivity and good selectivity in aqueous medium has been of great interest.¹ Chemosensors soluble in aqueous media are very interesting, because of the importance in revealing a number of biological processes, disease states and environmental pollutions.² 2,4,5-Triaryl-imidazoles are versatile compounds with application in medicine, due to their biological activity, and materials sciences, for their interesting optical properties. These properties can be tuned by careful selection of substituents at positions 2, 4 and 5: replacement of the aryl group by a heterocyclic group results in larger π-conjugated systems with improved optical properties for application in nonlinear optics, OLEDs, DNA intercalators, and chemosensors.³ In this communication, we report the synthesis of new phenanthroimidazoles, substituted at position 2 with (hetero)aryl groups of different electronic character, in order to evaluate their photophysical properties and chemosensory ability. The new derivatives were characterized by the usual techniques and a detailed photophysical study was undertaken. The evaluation of the compounds as fluorimetric chemosensors was carried out by performing titrations in acetonitrile and acetonitrile/water in the presence of relevant organic and inorganic anions, and of alkaline, alkaline-earth and transition metal cations.

The recognition and detection of ionic species has aroused great interest due to their important roles in many biological and environmental processes. Colorimetric chemosensors are molecules that allow naked-eye detection of ionic species without resource to any instrumentation, offering qualitative and quantitative information and are considered as one of the most effective analytical method for environmental monitoring, particularly in the detection of metal ions whose presence in the environment has serious consequences.¹ Research of sensors with good sensitivity and good selectivity in aqueous medium has been of great interest. Chemosensors soluble in aqueous media are very interesting, because of the importance in revealing a number of biological processes, disease states and environmental pollutions.² Hydrazone derivatives are versatile compounds with several applications such as in medicinal chemistry due to their vast biological activity and as optical (colorimetric and fluorimetric) sensing of anions and metal cations. Other applications in materials science include molecular switches, OLEDs, etc.³ In this communication, we report the synthesis of one hydrazone derivative, functionalized with an heterocyclic moiety, in order to evaluate its photophysical properties and chemosensory ability. The new derivative was characterized by the usual techniques and a detailed photophysical study was undertaken. The evaluation of the novel compound as a colorimetric chemosensor was carried out by performing titrations in acetonitrile and acetonitrile/water in the presence of relevant organic and inorganic anions, and of alkaline, alkaline-earth and transition metal cations. Acknowledgements: Thank are due to Fundação para a Ciência e Tecnologia (Portugal) and FEDER-COMPETE for financial support through Centro de Química (UID/QUI/00686/2013 and UID/ QUI/0686/2016), and a PhD grant to R.C.M. Ferreira (SFRH/BD/86408/2012). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased with funds from FCT and FEDER.   References: a) Batista, R. M. F.; Costa, S. P. G.; Raposo, M. M. M. J. Photochem. Photobiol. A: Chem., 2013, 259, 33. b) Thakur, B.; Amarnath, C. A.; Mangoli, S. H.; Sawant, S. N. Sens. Actuat. B, 2015, 207, 262. a) Patil, S.; Patil, R.; Fegade, U.; Bondhopadhyay, B.; Pete, U.; Suban, K. S.; Singh, N.; Basu, A.; Bendre, R.; Kuwar, A. Photochem. Photobiol. Sci., 2015, 14, 439. b) Udhayakumari, D.; Velmathi, S.; Boobalan, M. S.; Venkatesan, P.; Wu, S.-P. J. Luminescence, 2015, 158, 484. c) Alici, O.; Erdemir, S. Sens. Actuat. B, 2015, 208, 159. d) Hu, Y.; Zhang, J.; Lv, Y.-Z.; Huang, X.-H-; Hu, S.-li. Spectrochim. Acta Part A: Mol. Biomol. Spect., 2016, 157, 164. (a) Raposo, M. M. M.; García-Acosta, B.; Ábalos, T.; Calero; P.; Martínez-Manez, R.; Ros-Lis, J. V.; Soto, J. J. Org. Chem., 2010, 75, 2922. b) Santos-Figueroa, L. E.; Moragues, M. E.; Raposo, M. M. M., Batista, R. M. F.; Ferreira, R. C. M.; Costa, S. P. G.; Sancenón, F.; Martínez-Máñez, R.; Ros-Lis, J. V.; Soto, J. Tetrahedron 2012, 68, 7179-7186. c) Santos-Figueroa, L. E.; Moragues, M. E.; Raposo, M. M. M., Batista, R. M. F.; Ferreira, R. C. M.; Costa, S. P. G.; Sancenón, F.; Martínez-Máñez, R.; Ros-Lis, J. V.; Soto, J. Org. Biomol. Chem. 2012, 10, 7418-7428. d) Marín-Hernández, C.; Santos-Figueroa, L. E.; Sayed S.; Pardo, T.; Raposo, M. M. M., Batista, R. M. F.; Costa, S. P. G.;  Sancenón, F. Martínez-Máñez, R. Dyes Pigments, 2015, 122, 50.

The research on selective chromo-fluorogenic sensors for anions, cations and neutral molecules is an exciting topic with recent developments, especially in the possibility of using colorimetric/fluorimetric probes to sense both anions and cations in aqueous solution. In particular, heterocyclic systems which have the ability to act as the recognition unit as well as the signalling unit, are very interesting since variation of their absorption/fluorescence properties can happen during the recognition event. With careful design, for example by inclusion of additional heterocycles, the analyte recognition and overall photophysical properties can be improved, leading to higher sensitivity and selectivity.¹ Imidazole based chromophores have received increasing attention recently due to their distinctive optical properties and excellent thermal stabilities making them versatile systems for several applications such as optical chemosensors and two-photon absorbing molecules,² among other applications in materials and medicinal chemistry. For the recognition of certain anions, anthraquinone derivatives have been reported as suitable systems for colorimetric sensing since they are an example of electron acceptor groups that can be electronically connected with recognition units.³ Based on the above facts, herein we report the synthesis of one imidazo-anthraquinone, and its photophysical and chemosensory properties. The new derivative was obtained in good yield through a Radziszewski reaction between 1,2-diamino anthraquinone and an heterocyclic aldehyde, characterized by the usual techniques and a detailed photophysical study was undertaken. The evaluation of the compound as a colorimetric chemosensor was carried out by performing spectrophotometric titrations in ACN and ACN/H₂O in the presence of relevant organic and inorganic anions, and of alkaline, alkaline-earth and transition metal cations. Acknowledgements: Thank are due to Fundação para a Ciência e Tecnologia (Portugal) and FEDER-COMPETE for financial support through Centro de Química (UID/QUI/00686/2013 and UID/ QUI/0686/2016), and a PhD grant to R.C.M. Ferreira (SFRH/BD/86408/2012). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased with funds from FCT and FEDER.   a) M. Formica, V. Fusi, L. Giorgi, M. Micheloni, Coord. Chem. Rev., 2012, 256, 170-192. b) J.-F. Xu, H.-H. Chen, Y.-Z. Chen, Z.-J. Li, L.-Z. Wu, C.-H. Tung, Q.-Z. Yang, Sens. Actuators B, 2012, 168, 14-19. c) L. E. Santos-Figueroa, M. E. Moragues, E. Climent, A. Agostini, R. Martínez-Máñez, F. Sancenón, Chem. Soc. Rev., 2013, 42, 3489-3613. d) L. You, D. Zha, E. V. Anslyn, Chem. Rev., 2015, 115, 7840−7892. e) J. Li, S. Chen, P. Zhang, Z. Wang, G. Long, R. Ganguly, Y. Li, Q. Zhang, Chem. Asian J. 2016, 11, 136–140. a) E. Oliveira, R. M. F. Batista, S. P. G. Costa, M. M. M. Raposo, C. Lodeiro, Inorg. Chem., 2010, 49, 10847-10857. b) C. Marín-Hernández, L. E. Santos-Figueroa, S. Sayed, T. Pardo, M. M. M. Raposo, R. M. F. Batista, S. P. G. Costa, F. Sancenón, R. Martínez-Máñez, Dyes Pigments, 2015, 122, 50-58. c) Q. Zhang, X. Tian, Z. Hu, C. Brommesson, J. Wu, H. Zhou, J. Yang, Z. Sun, Y. Tian, K. Uvdal, Dyes Pigments, 2016, 126, 286-295. d) C. I. C. Esteves, M. M. M. Raposo, S. P. G. Costa, Dyes Pigments, 2016, 134, 258-268. a) R. M. F. Batista, E. Oliveira, S. P. G. Costa, C. Lodeiro, M. M. M. Raposo, Org. Lett., 2007, 9, 3201-3204. b) R. M. F. Batista, S. P. G. Costa, M. M. M. Raposo, J. Photochem. Photobiol. Chem., 2013, 259, 33-40. c) R. M. F. Batista, E. Oliveira, S. P. G. Costa, C. Lodeiro, M. M. M. Raposo, Supramol. Chem., 2013, 26, 71-80. d) R. M. F. Batista, S. P. G. Costa, M. M. M. Raposo, Sens. Actuators B: Chem., 2014, 191, 791-799. e) C. Marín-Hernández, L. E. Santos-Figueroa, M. E. Moragues, M. M. M. Raposo, R. M. F. Batista, S. P. G. Costa, T. Pardo, R. Martínez-Máñez, F Sancenón, J. Org. Chem., 2014, 79, 10752-10761.

Imine derivatives are an important class of compounds due their biological and optical properties making them suitable for several applications such as chemosensor, photochromic, and others.^1,2 In recent years the search for new colorimetric chemosensors for anions has been of great interest because of the role that ions play in chemical and biological processes.³ In this context and as part of an on-going research to develop efficient heterocyclic systems for photochromic and chemosensor applications⁴ we report in this communication the synthesis, the photophysical characterization and the chemosensor ability of pyrrolidene heterocyclic imines functionalized with aryl or naphthyl moieties.