The synthesis and fluorescence behaviour of new unsymmetrically mono-functionalized carboxy Ge, Ti and Sn phthalocynines Nkosiphile Masilela, Tebello Nyokong * Department of Chemistry, Rhodes University, Grahamstown 6140, South Africa article info Article history: Received 2 February 2011 Received in revised form 24 March 2011 Accepted 26 March 2011 Available online 2 April 2011 Keywords: Low symmetry phthalocyanines Monocarboxy phthalocyanines Germanium Titanium Tin Fluorescence quantum yields and lifetimes abstract This work reports on the synthesis and fluorescence behaviour of novel unsymmetrically substituted monocarboxy germanium ((OH) 2 GeMCPc, 3), titanium (OTiMCPc 4) and tin ((ac) 2 SnMCPc, 5) phthalo- cyanines. The fluorescence quantum yields ranged from 0.09 to 0.14. The fluorescence lifetimes were found to be higher for the complex with higher fluorescence quantum yield value. Higher fluorescence quantum yields and lifetimes were obtained for the (ac) 2 SnMCPc complex (5), followed by OTiMCPc complex (4), and the lowest fluorescence quantum yield and lifetime were observed for (OH) 2 GeMCPc (3). Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Metallophthalocyanines (MPcs) show promise for many appli- cations including in: photocatalysis [1e4], photo-electrocatalysis [5] and photodynamic therapy of cancer [6e10]. Mono-functionalized MPc complexes are of great interest since they can be coupled to various substrates by chemically binding one reactive substituent of the Pc, with the other binding sides being blocked with non reactive substituents [11,12]. It is also believed that low symmetry phthalo- cyanines have less tendencies to form aggregates compared to symmetrically tetrasubstituted Pcs which is a very useful and attractive property for these Pcs for their application as photosen- sitizers. For a good photosensitizer a molecule is required to be in its monomeric state for successful photo-induced energy and electron transfer [13e15]. Low symmetry bisthienylethene phtha- locyanines with photochromic properties have been reported [16,17]. The complexes showed potential for applications in photo- switching devices [17]. Recently our group has reported on selective coupling of a monocarboxy phthalocyanine complex on zinc oxide substrates for solar cells applications [15]. The photo-electro- chemical studies of a series of symmetrically carboxy phthalocya- nines displayed a lack of selective binding due to the presence of many carboxylic acid groups available for attachment on ZnO. The complexes also showed aggregation when they were bound to ZnO substrate, which lead to low power efficiencies compared to unsymmetrically monosubstituted carboxy Pc [15]. Other studies in our group have shown successful linking of nano particles such as quantum dots to low symmetry amino phthalocyanines for the improvement of Förster resonance energy transfer (FRET) as compared to symmetrically substituted carboxy Pcs [18]. However the disadvantage of working with low symmetry phthalocyanine complexes is the low yield that is obtained during the synthesis of the complexes [19]. The statistical condensation method of making low symmetry phthalocyanines results in a mixture of different compounds depending on the ratio of the two starting material used [20e23]. Separation of the various compounds formed during the synthesis to get the desired mono-functionalized Pc complex is a major and a crucial step during the purification of these complexes, resulting in low yields of the desired product due to loss during the separation. Herein we report on the synthesis and characterization of germanium, titanium and tin phthalocyanine complexes with only one reactive carboxy group as an electrophile. We investigate the fluorescence properties of these compounds in solution. Most low symmetry MPc complexes contain the common central metals such as Zn. In this work we use Ti, Ge and Sn as central metals, the use of the carboxy group is to allow coordination of biological molecules containing amino groups at a later state, the dieth- ylaminoethanethiol substituents were chosen to enhance solubility * Corresponding author. Tel.: þ27 46 6038260; fax: þ27 46 6225109. E-mail address: t.nyokong@ru.ac.za (T. Nyokong). Contents lists available at ScienceDirect Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig 0143-7208/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.dyepig.2011.03.026 Dyes and Pigments 91 (2011) 164e169