Orthogonal Coordination Chemistry of PTA toward Ru(II) and Zn(II) (PTA = 1,3,5-Triaza-7-phosphaadamantane) for the Construction of 1D and 2D Metal-Mediated Porphyrin Networks

Abstract

This work demonstrates that PTA (1,3,5-triaza-7-phosphaadamantane) behaves as an orthogonal ligand between Ru(II) and Zn(II), since it selectively binds through the P atom to ruthenium and through one or more of the N atoms to zinc. This property of PTA was exploited for preparing the two monomeric porphyrin adducts with axially bound PTA, [Ru(TPP)(PTA-κ P ) 2 ] ( 1 , TPP = meso -tetraphenylporphyrin) and [Zn(TPP)(PTA-κ N )] ( 3 ). Next, we prepared a number of heterobimetallic Ru/Zn porphyrin polymeric networks—and two discrete molecular systems—mediated by P,N -bridging PTA in which either both metals reside inside a porphyrin core, or one metal belongs to a porphyrin, either Ru(TPP) or Zn(TPP), and the other to a complex or salt of the complementary metal (i.e., cis,cis,trans -[RuCl 2 (CO) 2 (PTA-κ P ) 2 ] ( 5 ), trans -[RuCl 2 (PTA-κ P ) 4 ] ( 7 ), Zn(CH 3 COO) 2 , and ZnCl 2 ). The molecular compounds 1 , 3 , trans -[{RuCl 2 (PTA-κ 2 P,N ) 4 }{Zn(TPP)} 4 ] ( 8 ), and [{Ru(TPP)(PTA-κ P )(PTA-κ 2 P,N )}{ZnCl 2 (OH 2 )}] ( 11 ), as well as the polymeric species [{Ru(TPP)(PTA-κ 2 P,N ) 2 }{Zn(TPP)}] ∞ ( 4 ), cis,cis,trans -[{RuCl 2 (CO) 2 (PTA-κ 2 P,N ) 2 }{Zn(TPP)}] ∞ ( 6 ), trans -[{RuCl 2 (PTA-κ 2 P,N ) 4 }{Zn(TPP)} 2 ] ∞ ( 9 ), and [{Ru(TPP)(PTA-κ 3 P,2N ) 2 }{Zn 9 (CH 3 COO) 16 (CH 3 OH) 2 (OH) 2 }] ∞ ( 10 ), were structurally characterized by single crystal X-ray diffraction. Compounds 4 , 6 , 9 , and 10 are the first examples of so...

Stereoisomeric Control in [RuCl2(PTA)2(2L)] Complexes (2L=2py or bpy): From Theoretical Calculations to a 2+2 Metallacycle of Pyridylporphyrins

“…The metallacycle 10 was treated with excess Zn(CH 3 COO) 2 at room temperature, with the purpose of obtaining the corresponding zincated metallacycle trans,cis,cis ‐[RuCl 2 (PTA) 2 (Zn ⋅ 4′‐ cis DPyP)] 2 ( 10Zn ) that – similar to 11Zn – might be exploited as a flat molecular panel for the construction of higher‐order supramolecular assemblies, [67,69] Unfortunately, the reaction afforded an almost insoluble purple precipitate, most likely due to the establishment of multiple axial Zn−N(PTA) intermolecular interactions, [39] that could not be characterized. Nevertheless, the UV‐vis spectrum of a very diluted solution confirmed the insertion of zinc into the two porphyrin cores (Supporting Information).…”

“…In recent years we have actively investigated the chemistry of Ru(II)‐PTA compounds, preparing new species and finding systematic trends [6,36–40] . In particular – with the aim of preparing water soluble conjugates and metal‐mediated assemblies – we systematically explored the preparation of Ru(II)‐PTA derivatives with the imine ligands pyridine (py) and 2,2′‐bipyridine (bpy), [36,40] used as models for monodentate pyridyl‐linkers (e. g. 4,4′‐bpy or pyridylporphyrins) and for chelating diimine linkers, such as 4′‐methyl‐2,2′‐bipyridine‐4‐carboxylic acid (bpyAc) and 2‐(2′‐pyridyl)pyrimidine‐4‐carboxylic acid (cppH) (Figure 1), respectively [41–43] …”

“…[2,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] In recent years we have actively investigated the chemistry of Ru(II)-PTA compounds, preparing new species and finding systematic trends. [6,[36][37][38][39][40] In particular -with the aim of preparing water soluble conjugates and metal-mediated assemblies -we systematically explored the preparation of Ru(II)-PTA derivatives with the imine ligands pyridine (py) and 2,2'-bipyridine (bpy), [36,40] used as models for monodentate pyridyl-linkers (e. g. 4,4'-bpy or pyridylporphyrins) and for chelating diimine linkers, such as 4'-methyl-2,2'-bipyridine-4-carboxylic acid (bpyAc) and 2-(2'-pyridyl)pyrimidine-4-carboxylic acid (cppH) (Figure 1), respectively. [41][42][43] Whereas there are very few examples of Ru(II)-PTA coordination compounds in the literature with monodentate pyridine or azole ligands, [40] i. e. not included in polydentate moieties, [12,[44][45][46][47][48][49] those with chelating diimine ligands are relatively more abundant.…”

Investigating the reactivity of neutral water-soluble Ru(ii)–PTA carbonyls towards the model imine ligands pyridine and 2,2′-bipyridine

“…For this reason PTA metal compounds have been investigated as potential anticancer drugs, [3][4][5][6][7] and as homogeneous catalysts in aqueous solution or in biphasic aqueous-organic conditions. 2,[8][9][10] In addition, PTA-kP can bind also to other metal ions through the three hard N atoms, thus acting as a bridging ligand, 2, 11 and undergo N-protonation at relatively mild pH (in Ru(II) complexes PTA-kP has a pK a value of ca. 3), 12,13 thus altering the charge and solubility of its complexes.…”

“…15,17 We describe here the preparation and characterization of a series of new derivatives. The compounds trans,trans,trans- Cl (15), and cis,cis-[Ru(bpy)(CO) 2 Cl(PTA)]Cl (16) were either iden-tied in solution only (8,15,16) or isolated in low amounts (11). The X-ray molecular structures of 7, 11$H 2 O, and 12$7H 2 O are also reported, together with a comprehensive collection of the typical 31 P NMR chemical shi in Ru(II)-PTA complexes as a function of the trans ligand.…”