The investigation of ferrocenophanes has been effectively stimulated by the search for useful starting building blocks for the preparation of new organometallic complexes and functional materials, efficient catalyst components, and redoxactive modifiers of biomolecules.[1] The ability of ferrocenophanes to produce functional metallopolymers by ring-opening polymerization (ROP) provides a continuous momentum to the field.[2] The electronic properties of metallocene units embedded in ansa structures are of fundamental importance in determining their overall molecular properties (Scheme 1). However, in the majority of systems explored to date, the electronic communication between externally bridged cyclopentadienyl (Cp) rings was rather limited, as shown by structural and spectroscopic data. [3][4][5] Another approach to probing the effectiveness of electronic conjugation across a sandwich complex is the incorporation of a metallocene subunit into an otherwise fully pconjugated macrocycle. However, none of conjugated ferrocenophanes reported to date revealed features characteristic of macrocyclic aromaticity. [3][4][5] More recently, we have considered heterocyclic macrocycles of the general structure 1, combining the structural features of ansa-metallocenes and porphyrinoids.[6] To date, a number of bridged pyrrolic ansaferrocene, [7] ferrocene-calixpyrrole, [8] and ferrocene-calixphyrin [6,9] hybrids have been reported (e.g., 2), [6] which were based on a similar structural paradigm except that p conjugation in the oligopyrrin chain was interrupted by sp 3 -hybridized meso bridges.We have surmised that upon achieving complete conjugation in the oligopyrrin, the metallocene unit, occasionally described as a three-dimensional equivalent of p-electron aromatic units, [10] will contribute to metallomacrocyclic aromaticity in a similar fashion as various "two-dimensional" hetero-and carbocyclic rings commonly incorporated into porphyrinoid analogues.[11] Herein we report the synthesis and characterization of ferrocenothiaporphyrin 5 and dihydroferrocenothiaporphyrin 6, which possess macrocyclic antiaromaticity and aromaticity, respectively. These two systems provide evidence for direct transmission of p-electron conjugation across a d-electron metallocene.The title compound, ferrocenothiaporphyrin ([1-4,21-24,25,29h-25,29-dihydro-25,29-dicarba-27-thiapentapyrrin-25,29-diyl]iron(II)) 5, was obtained in a [3+1] macrocyclization reaction that involved 1,1'-bis[phenyl(2-pyrrolyl)methyl]ferrocene 3 and 2,5-bis[hydroxy(p-tolyl)-methyl]thiophene 4, which were condensed under Lindsey-type conditions (Scheme 2). After oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and column chromatography, the procedure afforded 5 as a dark brown compound in 9 % yield. Scheme 1. Incorporation of ferrocene into a porphyrinoid macrocycle.(1: X = N, NH, O, S; 2: R 1 = Me, R 2 = tolyl (Tol), 2a: R 1 = R 2 = H).Scheme 2. Synthesis and reactivity of 5 and 6 (R 1 = Ph, R 2 = Tol). The partial p-electron pathway is shown in bold.

Scheme 1. Incorporation of ferrocene into a porphyrinoid macrocycle. (1: X = N, NH, O, S; 2: R 1 = Me, R 2 = tolyl (Tol), 2a: R 1 = R 2 = H).Scheme 2. Synthesis and reactivity of 5 and 6 (R 1 = Ph, R 2 = Tol). The partial p-electron pathway is shown in bold.

Ferrocene‐containing porphyrinoids have been synthesized in which ferrocene‐1,1′‐diyl units are linked to a dipyrrin or thiatripyrrin to form macrocyclic structures. NMR spectroscopic evidence shows that these new systems adopt helical conformations that undergo an inversion process in solution. In addition, small amounts of unexpected scrambling products have been isolated and characterized, namely a dipyrrin‐bisferrocenophane and two expanded bis(ferrocene) macrocycles. The formation of these systems, which contain macrocyclic rings of different sizes, is a consequence of the structural flexibility of the ferrocene unit. Cyclic voltammetry shows that ferrocene oxidation is reversible in all the systems reported here, and that it is finely tuned by the properties of the ring system. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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