Selecting pyrazole-based silver complexes for efficient liquid crystal and luminescent materials Lorena Soria a, 1 , Paloma Ovejero a,1 , Mercedes Cano a, * , José A. Campo a,1 , M. Rosario Torres b, 2 , Cristina Núñez c, d, e , Carlos Lodeiro c, f a Departamento de Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain b CAI de Difracción de Rayos-X, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain c REQUIMTE-CQFB, Chemistry Department, Faculty of Science and Technology, University NOVA of Lisbon, 2829-516 Monte da Caparica, Portugal d Department of Inorganic Chemistry, Faculty of Chemistry, University of Santiago de Compostela, Spain e Department of Geographical and Life Sciences, Canterbury Christ Church University, CT1 1QU Canterbury, United Kingdom f ProteoMass Scientific Society, Madan Parque, Rua dos Inventores, 2825-182 Caparica, Portugal article info Article history: Received 21 February 2014 Received in revised form 2 April 2014 Accepted 5 April 2014 Available online xxx Dedicated to the memory of Prof.Dr. José Vicente Heras Castelló. Keywords: Luminescent silver complexes Liquid crystals Luminescent metallomesogens Pyrazole based complexes Bifunctional materials Molecular design abstract The liquid crystal and luminescent properties of two families of silver complexes (A ¼ [Ag(L) 2 ][NO 3 ] and B ¼ [Ag(L)(NO 3 )]) based on 3,5-alkyloxyphenyl, 3-pyridyl-5-alkyloxyphenyl and 3-alkyloxyphenyl substituted pyrazole ligands (L) were analysed on the light of the influence of factors as the stoichio- metric metal to ligand ratio or the nature of the substituents on the pyrazole ring. This latter is related to the presence of the pyridine groups or the symmetrical or asymmetrical alkylokyphenyl substitution. The interest of the research was focused on determining the molecular characteristics that optimise the mesomorphic properties/structure relationship. The thermal behaviour of A revealed that an “H” mo- lecular shape was an imperative factor to achieve the best mesomorphic properties, while the meso- morphism of B was clearly dependent on the number and/or on the symmetric or asymmetric alkyloxyphenyl substitution on the pyrazole ring. The fluorescent properties of both types of compounds were also examined and compared. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Molecular materials with properties like light emission or electronic transport have received significant attention due to their potential applications in the growing research field of displays, OLED’s, sensors, information storage, solar cells and active com- ponents for image and data treatment storage [1]. In particular, the combination of the supramolecular ordering of the mesophases with luminescent properties in the same material (giving rise to intrinsic fluoroforic liquid crystal materials) is of significant interest to generate new molecular electronics. In this context it is important to mention that the presence of certain metals like silver has been strategically used to achieve luminescent metallomesogens [2]. Previous works from our lab were focused on designing silver complexes supported by mesogenic or promesogenic pyrazole- based ligands. So, mono- or di-alkyloxyphenyl substituted pyr- azole compounds and the related pyridine functionalised ones were used towards different silver salts AgA (A ¼ NO 3 , BF 4 , PF 6 , CH 3 -p-C 6 H 4 SO 3 (PTS), CF 3 SO 3 (OTf)), giving rise to mesomorphic ionic complexes that exhibited SmA and SmC mesophases [3]. However due to the results were quite dispersed, because of the many variables included, we consider that a systematic study could be used as an important tool in order to determine the structure/ properties relationship. In addition, the analysis of the photo- luminescent properties of the compounds involved in this study could also be included to determine their potential ability as bifunctional materials. With that idea in mind we are interested in determining the characteristics of pyrazole-based silver metallomesogens, which lead to the optimisation of the mesomorphism. For this purpose we have selected a family of ionic silver com- plexes built with the following requirements: a) the use of pyrazole * Corresponding author. Tel.: þ34 91 394 4340; fax: þ34 91 394 4352. E-mail address: mmcano@quim.ucm.es (M. Cano). 1 Tel.: þ34 91 394 4340; fax: þ34 91 394 4352. 2 Tel.: þ34 91 394 4284. Contents lists available at ScienceDirect Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig http://dx.doi.org/10.1016/j.dyepig.2014.04.010 0143-7208/Ó 2014 Elsevier Ltd. All rights reserved. Dyes and Pigments xxx (2014) 1e10 Please cite this article in press as: Soria L, et al., Selecting pyrazole-based silver complexes for efficient liquid crystal and luminescent materials, Dyes and Pigments (2014), http://dx.doi.org/10.1016/j.dyepig.2014.04.010