Tetraoxaporphyrin Dication

Abstract

should be regarded as a binuclear sandwich complex having two four-electron donor p,q2-P2 ligands (i.e., 18 valence electrons (VE) per Rh atom), the bonding in the Co analogue 6 is more complicated. The X-ray structure analysis reveals two independent molecules per unit cell,1'21 each of whose Co-Co distances is ca. 3.1 A. In this case, the P,bridging ligand forms a "long" (similar to that of 2b) and a "short" (32-VE triple-decker with cyclo-P,?) rectangle, whose average P_P values correspond almost exactly to the distance of 2.38 A in the cubic (metallic) m~d i f i c a t i o n l '~~ of black phosphorus (z(P-P) = 2.45 A for 2b). The Rh-Rh' distance of 2b (3.324(1) A) is significantly longer than d ( M-M) for triple-decker complexes (2.63-2.73 A) containing a C~C I O -P~~~, middle deck and exhibiting metal-metal i n t e r a~t i o n ; [~.~] the average Rh-P value for 2b (2.416 A) is larger than that observed for 7 (2.335 A).[141 Experimental Procedure 2a.b: la (650mg, 2.2 mmol) [Isa] [lb (600 mg, 1.95 mmol) [I5b]] and P, (547 mg, 4.4 mmol) [483 mg, 3.9 mmol) were stirred in refluxing xylene (ca. 30 mL) for 8 h. The reaction solution (containing small amounts of insoluble components) was concentrated to 10 mL under oil-pump vacuum, treatedwith 3 g of AIZO3 (basic, activity II), and then dried under oil-pump vacuum to afford a freely flowing solid. Upon chromatography (column: 25 x 2.5 cm), excess P4 was eluted as a yellow forerun with pentane. Elution with pentane/toluene ( I : I ) then afforded Za,b as a yellow-orange fraction.After removal of the solvent under oil-pump vacuum, Za,b were obtained as spectroscopically pure, orange powders. Recrystallization from pentane (ca.-18°C) afforded Z a as needle-shaped and 2 b as cube-shaped, orange crystals. Yield Za: 207 mg (31Yo) [Zb: 190mg (3IYo)l.

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

“…Diprotonated porphyrin has a non planar structure mimicking that of non planar porphyrinic prosthetic groups [271]. Tetraoxaporphyrin dication, the oxygen analogue of porphyrin, has the highly symmetrical D 4h structure [272,273] which may be modulated through five redox stages [274]. The structural parameters of the three molecular species have been the object of a large number of computational studies all of which indicate that the stable forms of porphyrin and tetraoxaporphyrin have D 2h and D 4h geometries, respectively, when electron correlation is taken into account [275][276][277][278][279][280][281][282].…”

“…The structural parameters of the three molecular species have been the object of a large number of computational studies all of which indicate that the stable forms of porphyrin and tetraoxaporphyrin have D 2h and D 4h geometries, respectively, when electron correlation is taken into account [275][276][277][278][279][280][281][282]. The experimental [272,283,284] and calculated [275] bondlengths of the three macrocycles are reported in Figure 45.…”

Synthesis and Structure of Diboraporphyrinogenes

“…As for 5 and 8 (see below), the macrocycles 6 and 7 are air-and moisture-sensitive. Their 11 B NMR spectra exhibit broad signals at δ ϭ 43 ppm (6) and δ ϭ 42 ppm (7), which appear in the same region as that of the tetrathiatetraboraporphyrinogene B. [8] Because of the amino substituents at the boron atoms, the tetrathia-5,15-diboraporphyrinogenes 5Ϫ7 are electronically saturated due to the π interactions with the nitrogen atoms.…”

“…[6] They are oxidized to yield dicationic aromatic compounds having diatropic ring currents. [7] the 2,5-diborylthiophene derivative 9. Analogously, the mixed 5,10-diboraporphyrinogenes 15 and 16 are formed from 4 and 2,5-diborylfuran 11 and 2,5-diboryl-N-methylpyrrole 12, respectively.…”

Palladium‐Catalyzed Syntheses of Polyethynyl‐Substituted 2,2′‐Bithiophenes

“…Inverted [5] and expanded porphyrinoides [6] as well as porphycenes, hemiporphycenes, and corrphycenes [7] have been synthesized. Heterocyclic analogs of this class of compounds have also been reported [8].Prompted by the observation of Vogel, Schaffner and coworkers [9], which showed the potential of acetylenic and cumulenic porphycene derivatives as PDT agents, we investigated the syntheses of S-containing porphycene analogs, namely 21,23-dithiaporphycene and tetrathiaporphycene [ 101. The 2,2'-bithiophenes ( = 2,2'-bithienyls), the major component of the thiaporphycene system, have also been reported to possess interesting properties.…”