Regioselective Palladation of a Möbius Aromatic [28]Hexaphyrin(1.1.1.1.1.1) Pd II Complex

The four expanded p-benziporphyrins A,C-di-p-benzi[24]pentaphyrin(1.1.1.1.1), N-fused A-p-benzi[24]pentaphyrin, A,D-di-p-benzi[28]hexaphyrin(1.1.1.1.1.1), and A,C-di-p-benzi[28]hexaphyrin(1.1.1.1.1.1) were obtained in three-component Lindsey-type macrocyclizations. These compounds were explored as macrocyclic ligands and as potential aromaticity switches. A BODIPY-like difluoroboron complex was obtained from the A,C-di-p-benzi[24]pentaphyrin, whereas A,C-di-p-benzi[28]hexaphyrin yielded a Möbius-aromatic Pd(II) complex containing fused pyrrole and phenylene subunits. Conformational behavior, tautomerism, and acid-base chemistry of the new macrocycles were characterized by means of NMR spectroscopy and DFT calculations. Free base N-fused A-p-benzi[24]pentaphyrin showed temperature-dependent Hückel-Möbius aromaticity switching, whereas the A,C-di-p-benzi[28]hexaphyrin formed a Möbius-aromatic dication.

Section: The Hexaphyrin 8-hmentioning

confidence: 98%

Hückel and Möbius Expanded para‐Benziporphyrins: Synthesis and Aromaticity Switching

Szyszko

Sprutta

Chwalisz

et al. 2014

“…[29] Appealingly,t hese twisted conformations are intrinsically chiral, having potential applications in chirality sensing and asymmetriccatalysis. [30,31] In contrast, Group 11 metal ions generally provide Hückeltype complexes. Au III is unique and allows the formation of planarm ono-a nd bis-Au III metal complexesb yd ouble CÀH bond activation.…”

Section: Introductionmentioning

confidence: 99%

Metalated Hexaphyrins: From Understanding to Rational Design

Alonso

Pintér

Geerlings

et al. 2015

The heretofore unpredictable behavior of [26] and [28]hexaphyrins upon metalation has been elucidated through quantum chemical calculations. It is demonstrated that the molecular topology of Group 10 and Group 11 metal complexes of hexaphyrins depends on sensitive interplay between the intrinsic ligand strain and the metal-ligand interaction strength. As such, the aromaticity of the ligand and effective charge of the metal are revealed as key factors determining the binding mode and the preference for Möbius or Hückel structures. These findings offer a new perspective to rationalize experimental observations for metalated hexaphyrins. More importantly, the proposed guidelines could be useful for designing novel complexes of hexaphyrins, such as a hitherto unknown Möbius [26]hexaphyrin complex.

“…[2] Various ion-pairinga ssemblies with charge-bycharge and charge-segregated modes have been reported based on genuine p-electronic ions [2b,c,f] along with receptoranion complexes [2b,c,e] and cationic metal complexes [2d,g] as pseudo p-electronic ions. [10] BPMOsc an stabilizev arious transition metals in low andh igh oxidation states, because they combine both soft (P) and hard (O) Lewis base centers in one molecule. This strategy has been utilized in dipyrrolyldiketone boronc omplexes, [3] dipyrrolylnitrophenols, [4] and meso-hydroxy-substitutedp orphyrins (MHPs).…”

mentioning

confidence: 99%

“…This strategy has been utilized in dipyrrolyldiketone boronc omplexes, [3] dipyrrolylnitrophenols, [4] and meso-hydroxy-substitutedp orphyrins (MHPs). [10] BPMOsc an stabilizev arious transition metals in low andh igh oxidation states, because they combine both soft (P) and hard (O) Lewis base centers in one molecule. [7] An effective synthetic method for meso-aryl-substituted MHPs was reported by Arnold and co-workers, [8] followedby several related studies.…”

mentioning

confidence: 99%

“…[7] An effective synthetic method for meso-aryl-substituted MHPs was reported by Arnold and co-workers, [8] followedby several related studies. [10] BPMOsc an stabilizev arious transition metals in low andh igh oxidation states, because they combine both soft (P) and hard (O) Lewis base centers in one molecule. [9] Although peripheral modifications at the b-positions are essential for further developments in MHP chemistry,s ynthetic methodsf or such modifications have not been investigated.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Peripheral Modifications of meso‐Hydroxyporphyrins: Formation of π‐Electronic Anions and Ion‐Pairing Assemblies

Sasano

Haketa

Tanaka

et al. 2019

Phenyl groups were introduced at the b-positions proximal to the meso-hydroxy moiety in hydroxyporphyrin Ni II complexes by oxidized BINAP Pd II complexes. Ion-pairing assemblies of deprotonated p-electronic anions,a nionics ite of which was stabilized by the introduced phenyl moieties with ab ulky cation, were formed. They showedc harge-by-charge assemblies, assembly modes of which were modulated by the anionic building units.Assemblies of charged p-electronic systems can provide diverse functional materials based on the ordereda rrangement of ionic species. [1] Twoi ntrinsic modes of ion-pairing assemblies are observed in charge-by-charge assemblies with alternate stacking of oppositelyc harged species and charge-segregated assembliesw ith stacking of identically charged species (Figure 1a). [2] Various ion-pairinga ssemblies with charge-bycharge and charge-segregated modes have been reported based on genuine p-electronic ions [2b,c,f] along with receptoranion complexes [2b,c,e] and cationic metal complexes [2d,g] as pseudo p-electronic ions. The assembling modes can be controlledb yn oncovalent interactions, depending on designs of charged species and their combinations.I ng eneral,i ti sm uch more challenging to prepare p-electronic anions than p-electronicc ations,b ecause electron-rich anionic states exhibit high reactivity.O ne strategy for the preparation of p-electronic anionsi st he stabilization of an anionic site derivedfrom an acid unit introduced in the p systems( Figure 1b). This strategy has been utilized in dipyrrolyldiketone boronc omplexes, [3] dipyrrolylnitrophenols, [4] and meso-hydroxy-substitutedp orphyrins (MHPs). [2g, 5] MHPs are known as intermediates of heme degradation [6] andc an be oxidizedt or adicals pecies. [7] An effective synthetic method for meso-aryl-substituted MHPs was reported by Arnold and co-workers, [8] followedby several related studies. Stable radical species, as well as p-electronic cations,w ere isolated from MHPs,a nd their spectroscopic, structural, and theoretical propertiesw ere also examined. [9] Although peripheral modifications at the b-positions are essential for further developments in MHP chemistry,s ynthetic methodsf or such modifications have not been investigated. In this work, the introductiono fp henylg roups at the b-positions of MHPs was achieveda nd the resulting deprotonated p-electronica nions formedi on-pairinga ssemblies. Coupling reactions for the modifiedd erivatives werea ccomplished through isolated intermediates, in which the meso-O and b-C atoms coordinated to Pd II via an oxidized 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) ligand.B is-phosphine monooxides (BPMOs)w ith the general formula of R 1 R 2 PÀYÀP(O)R 3 R 4 (Y = spacer) are ligands that are often used in coupling reactions. [10] BPMOsc an stabilizev arious transition metals in low andh igh oxidation states, because they combine both soft (P) and hard (O) Lewis base centers in one molecule. [10a] In some cases,t he intermediateso fc oupling reactions can be isolate...