Luminescent metal complex subsituted tetrapyrroles

Porphyrins and phthalocyanines are aromatic macrocyclic compounds having four tetrapyrrolic rings attached through meso bridges. Phthalocyanines are known to be synthetic analogues of porphyrins and they differ from the latter with the presence of conjugated benzene ring to the pyrrolic entity and aza bridges at the meso positions. These aromatic compounds, having two dimensional and having 18-π electrons, are capable of forming coordination compounds with many elements in the periodic table. Phthalocyanines have flexible chemical systems which enable the modification of the ring in order to gain the required specific properties in many applications. High thermal stability, chemical strength, high coloration property, semiconductivity, photoconductivity, and catalytic activity are some superior properties and therefore, phthalocyanine and its derivatives have been investigated deeply and probable application fields in many diverse areas have been determined. Phthalocyanines are conjugated semiconductors. Since they are very strong against chemical reactions and temperature, they are being used in multi-layered organic light emitting diodes (OLEDs) as hole transport layer and electron barriers. Porphyrins, being the focus of many applications recently, are used as optoelectronics, magnetic materials, photoconductive materials, non-linear optical materials and photodynamic therapy, owing to their very stable macrocycle-pi systems. These applications are generally about the fact that porphyrins can absorb light in a stable and efficient manner in the visible and near-infrared regions of the optical spectrum. In this study, luminescent group-containing phthalocyanines' and porphyrins' syntheses are given. This study comprises three main sections. In the first part, we studied about conjugate binding of 8-hydroxyquinoline or 1,10-phenanthroline, both of which are mentioned of being luminescent materials in the literature, to the phthalocyanine nucleus. For this purpose, we proceeded through tetraaminophthalocyanine compound, and worked on Schiff base reaction by forming imine bridges to form tetrasubstituted 8-hydroxyquinoline-, 1,10phenanthroline-, and p-tolylterpyridine-containing phthalocyanines. However, the desired phthalocyanines could not be synthesized after the studies. To summarize what has been done in this part, we obtained 4-nitrophthalonitrile (3), which is used as the precursor of tetrasubstituted phthalocyanines, this compound was prepared from 4-nitrophthalimide (1), which was obtained by the nitration of phthalimide. The latter compound was subjected to ammoniacal solution to give 4-nitrophthalamide (2), which was reacted with thionyl chloride and dimethyl formamide to yield (3). Then we synthesized tetranitrophthalocyaninatozinc(II) (9) and by reduction of nitro groups, we obtained tetraaminophthalocyaninatozinc(II) (10). 5-formyl-8-hydroxyquinoline (4), which was considered to bind via imine bridge with compound (10), was prepared from 4-formyl-1,10-phenanthroline (8) in a single step by using commercial reagents. 4-Formyl-p-phenylterpyridine (7) compound was prepared from p-tolualdehyde and 2-acetylpyridine in three steps. All compounds are available in the literature, our compounds were characterized, and found to be compatible with those in the literature. In the second part of the study, meso-substituted porphyrins having luminescent groups were synthesized and characterized. For this purpose, we first prepared 3,4-dimethyl-5-carboxyethylpyrrole (11). Compound (11) was dimerized to give 3,3',4,4'-tetramethyl-5,5'-diarboxyethyldipyrromethane (12), which, on breaking the carboxy esters, transformed to 3,3',4,4'tetramethyldipyrromethane (13). Secondly, the relevant aldehyde was prepared from bromination, alkylation and formlylation of flourene in three steps to finally give 7-bromo-9,9-bis(2-ethyllhexyl)fluoren-2yl-carbaldehide (16). The metal-free porphyrin (22) was synthesized by DDQ-oxidation of porphyrinogen precursor, which was prepared by the condensation of compounds 13 and 16. 1H-NMR spectrum displays the characteristic intracyclic NH protons, usual for phthalocyanines and porphyrins, at -2,2 ppm and the ones bound to meso carbons at 10 ppm. The compound (22) was converted to metalloporphyrin (23) with Pt(acac)2. In the 1H-NMR spectrum of compound (23), the disappearance of high-field NH protons supports the metallation. Similarly, by starting from 4,8-dihydroxyquinoline-2-carboxylic acid, 5-chloro-8-tosyloxyquinoline (14c) was synthesized in three steps. Then this compound was coupled with Suzuki-Miyaura coupling reaction to (9,9-bis(2-ethyllhexyl)-7-(trimethylsilyl)-9H-fluoren-2-yl)boronic acid (18) to yield 2-(8-tosyloxyquinolin-5-yl)-7-trimethylsilyl-9,9-bis(2-ethylhexyl)fluorene (19). After iodination of trimethylsilane of compound (19), it was boronated to give 2-(8-tosyloxyquinolin-5-yl)-7-(4,4,5,5-tetramethyldioxoboran-2-yl)-9,9-bis(2-ethyllhexyl)lfluorene (21). The 1H-NMR spectrum of compound (21), the presence of aromatic and aliphatic protons coming from the main compound and methyl protons at 1,4 ppm (coming from the tetramethylborolane entity) show the successful preparation of boronic ester derivative. Compounds (21) and (23) were again coupled to each other with Suzuki-Miyaura coupling. 1H-NMR spectrum shows the protons coming from compound (23) and the quinoline and tosyl moieties coming from compound (21), which tells us that the coupling has been realized. In addition, the mass spectrum also provides the view of successful synthesis of the compound. In the third part, we used asymmetric phthalocyanine approach in order to increase the solubility and to obtain metal complex-type luminescent phthalocyanines. To increase the solubility, we synthesized an asymmetric phthalocyanine having hexylthio groups and [Ru(bpy)2(phen)]2+ complex. The precursor compounds and main products were characterized and spectral properties were analyzed. The results obtained supports the view of synthesis of the desired phthalocyanine. To summarize the studies done in this chapter, we first synthesized 4-(nitro-4-phenoxy)phthalonitrile (25) and 4-(hexylthio)phthalonitrile (26) according to literature methods and we then used these two phthalonitrile compounds in 1:4 ratio to give the asymmetric phthalocyanine derivatives. After required purifications were done the desired asymmetric phthalocyanine (27) were isolated The 1H-NMR spectrum of compound (27) displays aliphatic protons in the 0,85-1,60 ppm range and aromatic protons in the 6,62-8,26 ppm range. FT-IR spectrum of compound (27) has vibration modes at 2923-2853 cm-1 (alkyl groups) and vibrations at 1586 and 1338 cm-1 due to nitro group. This verifies the presence of both groups on the same phthalocyanine ring. The nitro groups of compound (27) were reduced to give compound (28). The presence of, in the FT-IR spectrum of compound (28), -NH2 vibration modes at 3327 and 3196 cm-1 and deformation bands at 1601 cm-1, but the absence of nitro group peaks at 1582 and 1345 cm-1, tells us that the reduction has been successfully completed. Compound (28) was reacted with the 4-formyll-1,10-phenantroline (8) to give compound (29). Then compound (30) was synthesized with reaction of commercially available Ru(bpy)2Cl2. Since the solubilities of compounds (29) and (30) are poor, the recorded 1H-NMR spectra had quite broad peaks and no interpretations could be made. However, UV-Vis spectra and mass measurements support the formation of the compounds. UV-Vis spectrum shows three peaks at 356, 686 and 280 nm, the latter being due to phenanthroline and ruthenium complex. Lastly, we investigated the fluorescent properties of compound (30) in a comparative manner. For this purpose, compound (29) and model compound [Ru(bpy)2(phen)]Cl2 were investigated in terms of their fluorescent properties. We observed that compounds (29) and (30) had their classical phthalocyanine-related fluorescent property, along with a new one due to [Ru(bpy)2(phen)]2+ complex.