Porphyrinoids DOI: 10.1002/ange.200904289 Helical Bis(N-Confused Porphyrins) with Subunits Fused by Double Orthometalation with Platinum: Adaptability of an Apparently Rigid System** Piotr J. Chmielewski,* Bartosz Durlej, Marta Siczek, and Ludmila Szterenberg Modifications of the interior or periphery of porphyrins allow major alteration or fine tuning of the properties of the system, such as cation- or anion-binding ability, redox potential, absorption, emission, as well as many other properties. Porphyrin subunits can be also relatively easily linked into larger two- and three-dimensional arrays, thus extending the possibility of their application as biomimetic models, cata- lysts, and materials for the transport of charge, molecules, and ions. Among the covalently [1] and coordinately [2] linked oligomers, the most attractive class is constituted by the systems in which the subunits are directly linked. [3] The interaction between delocalized p-bond systems appears to be strongest when the b-pyrrole carbon atoms of the porphyrins are linked. An important feature of b–b-linked bis(porphyr- ins) is their intrinsic axial chirality. However, the stability of the configuration requires restriction of the rotation around the b–b-bond. This restriction can be provided by the appropriate choice of metal ion that coordinates within both macrocyclic cores. [4] The external nitrogen atom of the confused pyrrole in N-confused porphyrin (NCP) 1 [5] and some of its derivatives [6] and complexes [7] can act as a donor site. [8] In the readily obtainable bis(N-confused porphyrin) 2, [9] a cis-oriented system of two external nitrogen atoms can potentially serve as a chelating ligand, and coordination of an inert metal ion in this site may prevent rotation and preserve configuration of the molecule. Platinum(II) is thus a metal ion of choice because of its tendency to form inert cis complexes that consist of a five-membered chelate ring. Reaction of bis(NCP) 2 with [Pt(PhCN)Cl 2 ] yields two isomeric platinum-containing complexes with different coor- dination modes (Scheme 1). Heating 2 at reflux with an equimolar amount of [Pt(PhCN) 2 Cl 2 ] in the presence of potassium carbonate in toluene for two days resulted in formation of 3 as the main product (about 50 %), as well as the monoplatinated insertion product 4 (10%). In both cases, the composition of the complex was established by ESI MS (m/z 1532), which indicates the presence of one platinum ion and one bis(NCP) unit. Compound 3 constitutes the first example of a bis(porphyrinoid) complex that consists of a metal ion coordinated by double orthometalation. [10] The twofold symmetry of the 1 H NMR spectrum of 3 (CDCl 3 , 213 K) reveals the same coordination mode for both subunits. The higher-field signals of protons bound to the internal carbon atom C21 at d = 3.41 ppm and those attached to the internal nitrogen atoms N22 and N24 (d = 1.19 and d = 0.05 ppm, respectively) indicate that the porphyrin cores are not occupied by metal ions. A doublet signal at d = 8.10 ppm with 4 J = 1.8 Hz is attributed to the meta proton in the vicinity of the deprotonated coordinating carbon atom of the para-tolyl substituents on C20 of both subunits. This Scheme 1. External and internal metalation of bis(NCP) 2 with platinum(II), insertion of silver(III) into the externally platinated bis(NCP) 3, and oxidative addition of iodine or iodoalkyls to 3. [*] Prof. P. J. Chmielewski, B. Durlej, M. Siczek, Dr. L. Szterenberg Department of Chemistry,University of Wrocław F. Joliot-Curie Street 14,50 383 Wrocław (Poland) Fax: (+ 48) 71-32-82348 E-mail: pjc@wchuwr.pl [**] This work was supported by the Ministry of Science and Higher Education under Grants PBZ-KBN-118/T09/2004 and N N204 029035. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.200904289. Zuschriften 8892  2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. 2009, 121, 8892 –8895