Synthesis, electrochemical and photophysical properties of covalently linked porphyrin–polyoxometalates

Abstract

Two covalently linked porphyrin-polyoxometalate hybrids have been prepared: an Anderson-type hexamolybdate [N(C(4)H(9))(4)](3)[MnMo(6)O(18){(OCH(2))(3)CNHCO(ZnTPP)}(2)] with two pendant zinc(II)-tetraphenylporphyrins, and a Dawson-type vanadotungstate [N(C(4)H(9))(4)](5)H[P(2)V(3)W(15)O(59){(OCH(2))(3)CNHCO(ZnTPP)}] with one porphyrin. Electrochemical studies show independent redox processes for the organic and inorganic parts at usual potentials. Photophysical studies reveal an electron transfer from the excited porphyrin to the Dawson polyoxometalate, but not to the Anderson polyoxometalate. Time resolved absorption spectroscopy allows the identification of the electron transfer pathways and the determination of the time constants.

Covalent Attachment of Thiophene Groups to Polyoxomolybdates or Poly­oxotungstates for the Formation of Hybrid Films

“…We have initiated a few years ago a study on polyoxomolybdates with grafted BPs, starting with Mo V derivatives and then going to Mo VI . [10] Three polyoxomolybdates have been isolated with Mo VI ions and alendronate ligands [R = (CH 2 ) 3 NH 2 , Ale, Scheme 1], which formation is highly dependent of the pH value: at pH = 7.5 the mononuclear POM [(MoO 2 )(Ale) 2 ] 6-[Mo(Ale) 2 ], [11] at pH = 4.5 the hexanuclear [(Mo 3 O 8 ) 2 O-(Ale) 2 ] 6-[Mo 6 (Ale) 2 ], [12] and at pH = 3.0 the dodecanuclear [(Mo 3 4 ]. [13] This family of hybrid POMs possesses both photochromic [13] and anticancer properties.…”

“…Another promising approach is the introduction of pendant groups which can induce the formation of gels, [6] of vesicles, [7] or can be involved in polymerization reactions. [8] Among the variety of organic molecules that can be covalently grafted on POM cores, bisphosphonates (BPs) with the general formula RC(OH)(PO 3 H 2 ) 2 are particularly (C 3 H 6 NH 2 CH 2 C 4 H 3 S)PO 3 ) 2 ] 14-[M = Ni, Co; M 7 (AleThio) 2 ]. Salts soluble in organic solvent were prepared by cation-exchange with bis(triphenylphosphine)iminium ions.…”

“…The introduction of organic ligands in these fully inorganic species not only increases their structural diversity but also can bring additional properties to the POMs and facilitates their processing into functional devices. [1] For example the modification of Anderson-type [MnMo 6 9-POMs by trisalkoxo ligands bearing functional group allows their grafting on surface, [2] brings additional photophysical, [3] photochromic, [4] or biological [5] properties. Another promising approach is the introduction of pendant groups which can induce the formation of gels, [6] of vesicles, [7] or can be involved in polymerization reactions.…”

Covalent hybrids based on Re(i) tricarbonyl complexes and polypyridine-functionalized polyoxometalate: synthesis, characterization and electronic properties

“…5 It has been applied to various POM structures (Lindqvist, Anderson and Dawson) 6 and the grafting reaction has been extensively studied. 7 While the use of diol--amide has been shown to induce electronic communication between the sub--unit of the prepared hybrids, 5c, 8 the use of triol such as tris--(hydroxymethyl) aminomethane (TRIS) has proven to be a viable route for the grafting of various moieties with limited electronic communication between the constitutive units, 9 in a true supramolecular approach. 10 We and others have used TRIS functionalized POMs to prepare polymeric 11 and discrete coordination species by introducing polypyridine ligands via an amide 12 or an imine 13 group.…”

Transition-metal-substituted polyoxometalate derivatives as functional anti-amyloid agents for Alzheimer’s disease

“…However, few inorganic agents have been reported that can inhibit Ab amyloid formation [6][7][8][9][10][11] . Polyoxometalates (POMs) are early transition metal oxide clusters (especially Mo, W and V) with high oxidation states, and they are used for constructing molecular architectures with potential applications 16 , for example, in catalysis 17 , magnetic materials 18 , chiral recognition 19 or nanocomposites 20 . Furthermore, POMs are promising candidates for drug-carrier approaches on the way to new composite drugs because they have long been known for their multifaceted bioactivity that encompasses antiviral, anticancer, antibacterial and herbicidal properties 21 .…”