Ionically bound metalloporphyrin pairs on solid polymer support

Abstract

ABSTRACT:The present work demonstrates a simple and elegant strategy by which synthetically simple porphyrins are grafted on solid polymer support to generate porphyrin pairs held together by strong coulombic forces. Metalloporphyrins of tetra(4-pyridyl)porphyrins (MTPyP) were reacted with chloromethylated polystyrene (PS) beads to get covalently bound monocationic porphyrins on the polymer support (PS-MTPyP ). These were then converted to their tetracationic species (PS-MTMe 3 PyP 4 ) by exhaustive quaternisation, using CH 3 I. IONICALLY BOUND METALLOPORPHYRIN PAIRS ON SOLID POLYMER SUPPORTBiological relevance and varied chemical utilities have made porphyrins in their dimeric/oligomeric form very interesting systems [1][2][3][4][5][6][7][8]. Selective positioning of such dimers and tetramers in the protein envelope is crucial in several life processes. We have demonstrated that considerable electronic and redox tuning of porphyrins is possible by grafting or incorporating them in polymer matrices and also by varying the mode of association between the host matrix and the pigment [9]. We have also attempted to model a few enzyme functions by making use of such a 'polymer effect' and utilising the easy workability of solid polymerimmobilised porphyrins [10][11][12]. In this communication we demonstrate a simple and elegant method by which novel porphyrin pairs could be grafted on a solid polymer surface and present the possibility of generating a wide variety of both homo-and hetero-porphyrin pairs associated through strong coulombic interaction.The strategy for developing the porphyrin pairs involves interacting the surface-functionalised solid polymer with porphyrins having reactive peripheral groups to affect initially a covalent linkage and then converting the grafted porphyrin moieties to tetracationic species and subsequently making them bind coulombically with tetraanionic porphyrins. The reaction process involved in the porphyrin pair generation is depicted in Scheme 1. The polymer support employed for the purpose was Merrifield resin (PS), which is divinylbenzene cross-linked polystyrene functionalised at the surface by chloromethylation containing 2.0 meq of Cl/g of polymer. The porphyrins used for initial grafting were either free-base or metalloderivatives of 5,10,15,20-tetra-4-pyridylporphyrin (MTPyP, M = H 2 , Mn, Cu, Zn, Ag), which were prepared by reported procedures [13,14]. The reaction involved for the grafting process was quaternisation of pyridyl moieties of MTPyP with the surface-CH 2 Cl functions of PS in dimethylformamide (DMF) medium (80°C, 72 h) (Step I in Scheme 1). A typical reaction process involved reacting 1 g of PS with 100 ml of a dilute porphyrin solution of 1 mM strength. The immobilisation of the porphyrin was evident from the characteristic colour formation on the polymer surface, which was persistent and unleachable with any solvent, whether polar or nonpolar, even under boiling condition. Spectrophotometric estimation showed that the extent of MTPyP uptake was in the range ...

Anti-infective photodynamic biomaterials for the prevention of intraocular lens-associated infectious endophthalmitis

“…This leaves up to three positively-charged pyridinium groups to interact with water through hydrogen bonding, resulting in a hydrophilic surface. Previous studies into ionically bound metalloporphyrin pairs on solid polymer supports yielded comparatively low uptake of TMPyP onto polystyrene, indicating that the porphyrins in all probability stayed widely separated on the polymer surface [45,46]. The authors concluded that grafting of the pyridyl porphyrins was expected to be through quaternization at one of the pyridinium moieties only, as linkage at more than one pyridinium function would cause severe steric problems between the porphyrin and the polymer support on immobilization [46].…”

“…Previous studies into ionically bound metalloporphyrin pairs on solid polymer supports yielded comparatively low uptake of TMPyP onto polystyrene, indicating that the porphyrins in all probability stayed widely separated on the polymer surface [45,46]. The authors concluded that grafting of the pyridyl porphyrins was expected to be through quaternization at one of the pyridinium moieties only, as linkage at more than one pyridinium function would cause severe steric problems between the porphyrin and the polymer support on immobilization [46]. The molecular weight of TMPyP (1363.6 g mol À1 ), the bulky nature of the pyridinium moieties, and the repulsion between these moieties prevent the porphyrin molecules from attaching to every free carboxylate group.…”

Photosensitizing properties of ionic porphyrins immobilized on functionalized solid polystyrene support

“…The ability of water‐soluble tetrasodium salt of meso –tetrakis(4‐sulfonatophenyl)porphyrins (H 2 TPPS) and some of its metalloderivatives (MTPPS) to photogenerate 1 O 2 has been demonstrated recently 15. We have been interested in developing polymer‐immobilized metalloporphyrins to model efficient enzyme functions by employing MTPPS and also in demonstrating the polymer effect on the porphyrin moieties 16–21. In the present study, we report the photosensitizing properties of some of such metalloporphyrins anchored on a functionalized solid polystyrene (PS) surface.…”