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Ground-state and time-dependent density functional theory (TDDFT) calculations with the long-range-corrected, Coulomb-attenuating CAMY-B3LYP exchange-correlation functional and large, all-electron STO-TZ2P basis sets have been used to examine the potential "inverse hypercorrole" character of meso-p -nitrophenyl-appended dicyanidocobalt(III) corrole dianions. The effect is most dramatic for 5,15-bis( p -nitrophenyl) derivatives, where it manifests itself in intense NIR absorptions. The 10-aryl groups in these complexes play a modulatory role, as evinced by experimental UV-visible spectroscopic and electrochemical data for a series of 5,15-bis( p -nitrophenyl) dicyanidocobalt(III) corroles. TDDFT (CAMY-B3LYP) calculations ascribe these features clearly to a transition from the corrole's a 2u -like HOMO (retaining the D 4h irrep used for metalloporphyrins) to a nitrophenyl-based LUMO. The outward nature of this transition contrasts with the usual phenyl-to-macrocycle direction of charge transfer transitions in many hyperporphyrins and hypercorroles; thus, the complexes studied are aptly described as inverse hypercorroles.

A mono-DMSO cobalt meso -CF 3 corrole, formulated as (CF 3 ) 3 CorCo(DMSO), where (CF 3 ) 3 Cor is the trianion of 5,10,15-tris(trifluoromethyl)corrole, was synthesized and characterized as to its spectral and electrochemical properties in nonaqueous media with a focus on its coordination chemistry and electronic structure. Cyclic voltammetric measurements showed more facile reductions and difficult oxidations compared to the cobalt triarylcorrole possessing p -CF 3 Ph units at the meso -positions, a result consistent with the enhanced inductive effect of the electron-withdrawing trifluoromethyl substituents linked directly at the meso -carbon atoms of the macrocycle. The effects of DMSO, pyridine, and cyanide anions (CN - ) on the electrochemistry and spectral properties of the compound were investigated, and it was found that only two molar equivalents are needed to form the bis-CN adduct, which exhibited two 1-electron oxidations at 0.27 and 0.95 V vs saturated calomel electrode (SCE) in CH 2 Cl 2 /0.1 M TBAP. The sites of electron transfer in the first oxidation and reduction were investigated by spectroelectrochemistry and confirmed that the first electron addition affords a Cor 3- Co II complex under all solution conditions independent of the initial coordination and/or electronic configuration ( i.e ., innocent Cor 3- Co III or noninnocent Cor •2- Co II ). In contrast, data for the first oxidation suggests that the site of electron abstraction (ligand or metal) depended upon coordination of the neutral and in situ generated complexes under the various solution conditions, leading to a Co(IV)-corrole 3- product for both the bis-pyridine and bis-cyanide adducts.

A series of cobalt nitrophenylcorroles were spectrally characterized in CH 2 Cl 2 , and under certain solution conditions, several compounds were shown to exhibit hypercorrole spectra resulting from charge transfer interactions from the corrole π-system to the redox-active meso -NO 2 Ph substituents. The resulting spectral pattern has not previously been reported for metallocorroles and in the case of the cobalt derivatives was shown to depend upon the number and position of the meso -nitrophenyl groups on the macrocycle, the position of the NO 2 substituent on the meso -phenyl ring(s) ( para or meta ), and the electronic structure of the corrole, which can exist in its innocent or noninnocent form depending in large part upon the type and number of axial ligands. Cobalt corroles bearing p -nitrophenyl groups at the 5,15- or 5,10,15-positions of the macrocycle exhibited the most marked hypercorrole spectra under solution conditions where the complex was innocent (i.e., Cor 3- Co III ), and a systematic analysis of the spectral data suggests the root of this perturbation to be a corrole-to-aryl interaction (i.e., ligand-to-ligand charge transfer or LLCT). The largest interaction between the π-system and the NO 2 Ph substituents was seen upon coordination of anionic cyanide (CN - ) axial ligands to the Co(III) center of the bis-(CN - )-5,15-dinitrophenyl derivative, resulting in a cobalt hypercorrole spectrum where the broad Q-band was red-shifted even further into the NIR region and located at 795 nm in CH 2 Cl 2 and 827 nm in pyridine. Cyclic voltammetry of the bis-CN - adducts showed that the first electrons are added to the LUMOs of the p -NO 2 Ph substituents rather than the corrole, while the same orbitals for the mono-CN - adducts are nearly degenerate. This redox behavior contrasts with what is seen for the noninnocent nitrophenyl corroles having "normal" unperturbed UV-vis spectra where the first reduction involves the π-system of the macrocycle, followed by reduction of the p -NO 2 Ph groups at more negative potentials.

A series of "N 2 O 2 -type" manganese dipyrrin-bisphenols (DPP), formulated as (Ar)DPPMn, where Ar = pentafluorophenyl (F 5 Ph), phenyl (Ph), or mesityl (Mes), were electrochemically and spectroscopically characterized in nonaqueous media with and without added anions in the form of tetrabutylammonium salts (TBAX where X = ClO 4 - , PF 6 - , BF 4 - , F - , Cl - , OH - , or CN - ). Two major one-electron reductions are observed under most solution conditions, the first of which is assigned as a Mn III/II process and the second as electron addition to the π-ring system as confirmed by spectroelectrochemistry. Each Mn III complex also exhibits one or two one-electron oxidations, the exact number depending upon the positive potential limit of the electrochemical solvent. The two oxidations are separated by 580-590 mV in CH 3 CN containing 0.1 M TBAPF 6 and are assigned as π-ring-centered electron transfers to stepwise form a (Ar)DPPMn III π-cation radical and dication under these solution conditions. Comparisons are made between redox properties of (Ar)DPPMn and manganese(III) porphyrins, corroles, and corrolazines each of which contains an innocent trianionic complexing ligand. The redox behavior and spectroscopic properties of [(Ar)DPPMn] n where n = 0, -1, or +1 are also compared to that of other structurally related [(Ar)DPPM] n complexes under similar solution conditions where M = Co II , Cu II , B III , or Au III .

Three mono-CN ligated anionic cobalt A 3 -triarylcorroles were synthesized and investigated as to their spectroscopic and electrochemical properties in CH 2 Cl 2 , pyridine (Py), and dimethyl sulfoxide (DMSO). The newly synthesized corroles provide the first examples of air-stable cobalt corroles with an anionic axial ligand and are represented as [(Ar) 3 CorCo III (CN)] - TBA + , where Cor is the trivalent corrole macrocycle, Ar is p -(CN)Ph, p -(CF 3 )Ph, or p -(OMe)Ph, and TBA + is the tetra- n -butylammonium (TBA) cation. Multiple redox reactions are observed for each mono-CN derivative with a key feature being a more facile first oxidation and a more difficult first reduction in all three solvents as compared to all previously examined corroles with similar meso- and β-pyrrole substituents. Formation constants (log K ) for conversion of the five-coordinate mono-CN complex to its six-coordinate bis-CN form ranged from 10 2.8 for Ar = p -(OMe)Ph to 10 4.7 for Ar = p -(CN)Ph in DMSO as determined by spectroscopic methodologies. The in situ generated bis-CN complexes, represented as [(Ar) 3 CorCo III (CN) 2 ] 2- (TBA + ) 2 , and the mixed ligand complexes, represented as [(Ar) 3 CorCo III (CN)(Py)] - TBA + , were also investigated as to their electrochemical and spectroscopic properties. UV-visible spectra and electrode reactions of the synthesized mono-CN derivatives are compared with the neutral mono-DMSO cobalt corrole complexes and the in situ generated bis-CN and bis-Py complexes, and the noninnocent (or innocent) nature of each cobalt corrole system is addressed. The data demonstrate the ability of the CN - axial ligand(s) to stabilize the high-valent forms of the metallocorrole, leading to systems with innocent macrocyclic ligands. Although a number of six-coordinate cobalt(III) corroles with N-donor ligands were characterized in the solid state, a dissociation of one axial ligand readily occurs in nonaqueous solvents, and this behavior contrasts with the high stability of the currently studied bis-CN adducts in CH 2 Cl 2 , pyridine, or DMSO. Linear free energy relationships were elucidated between the meso -phenyl Hammett substituent constants (Σσ) and the measured binding constants, the redox potentials, and the energy of the band positions in the mono-CN and bis-CN complexes in their neutral or singly oxidized forms, revealing highly predictable trends in the physicochemical properties of the anionic corroles.

A new series of cobalt A 3 -triarylcorroles were synthesized and the compounds examined as to their electrochemical and spectroscopic properties in CH 2 Cl 2 or dimethyl sulfoxide (DMSO) containing 10 different anions added to the solution in the form of tetrabutylammonium salts. The investigated anions were PF 6 - , BF 4 - , HSO 4 - , ClO 4 - , Br - , I - , Cl - , OAc - , F - , OTs - , and CN - , all but three of which were found to facilitate reduction of the cobalt corrole in dilute CH 2 Cl 2 solutions, as determined by a combination of UV-vis spectroscopy and spectroelectrochemistry. The synthesized corroles are represented as (Ar) 3 CorCo(DMSO), where Ar is a meso -phenyl group containing one of 10 different electron-donating or -withdrawing substituents. The axial DMSO ligand was found to dissociate in dilute (10 -5 M) CH 2 Cl 2 solutions, but this was not the case at the higher electrochemical concentration of 10 -3 M, where the investigated corroles exhibit a rich redox reactivity, undergoing up to five reversible one-electron-transfer reactions under the different solution conditions. The reversible half-wave potentials for generation of the singly oxidized corroles varied by over 1.0 V with a change in the electron-donating or -withdrawing meso -phenyl substituents and type of anion added to the solution, ranging from E 1/2 = 0.83 V in one extreme to -0.42 V in the other. Much smaller shifts in the potentials (on the order of ∼210 mV) were observed for the reversible first reduction as a function of changes of the anion and/or corrole substituents, with the only exception being in the case of CN - , where the E 1/2 values in CH 2 Cl 2 ranged from +0.08 V in solutions containing 0.1 M TBAClO 4 to >-1.8 V upon the addition of CN - .

Three cobalt dipyrrin-bisphenol (DPPCo) complexes with different meso-aryl groups (pentafluorophenyl, phenyl, and mesityl) were synthesized and characterized based on their electrochemistry and spectroscopic properties in nonaqueous media. Each DPPCo undergoes multiple oxidations and reductions with the potentials, reversibility, and number of processes depending on the specific solution conditions, the specific macrocyclic substituents, and the type and number of axially coordinated ligands on the central cobalt ion. Theoretical calculations of the compounds with different coordination numbers are given in the current study in order to elucidate the cobalt-ion oxidation state and the innocence or noninnocence of the macrocyclic ligand as a function of the changes in the solvent properties and degree of axial coordination. Electron paramagnetic resonance spectra of the compounds are obtained to experimentally assess the electron spin state. An X-ray structure of the six-coordinate complex is also presented. The investigated chemical properties of DPPCo compounds under different solution conditions are compared to those of cobalt corroles, where the macrocycle and metal ion also possess formal 3- and 3+ oxidation states in their air-stable forms.

A series of bis(pyridine)cobalt corroles with one or three nitrophenyl groups on the meso positions of the corrole macrocycle were synthesized and characterized as to their electrochemical and spectroscopic properties in dichloromethane, benzonitrile, and pyridine. The potentials for each electrode reaction were measured by cyclic voltammetry and the electron-transfer mechanisms evaluated by analysis of the electrochemical data combined with UV-visible spectra of the neutral, electroreduced, and electroxidized forms of the corroles. The proposed electronic configurations of the initial compounds and the prevailing redox reactions involving the electroactive central cobalt ion, the electroactive conjugated macrocycle, and the electroactive meso-nitrophenyl groups are all discussed in terms of solvent binding and the number of the nitrophenyl groups and other substituents on the meso-nitrophenyl rings of the compounds.

The electrochemistry and spectroelectrochemistry of four tetrapositively charged and two tetranegatively charged porphyrins were characterized in two nonaqueous solvents (dimethyl sulfoxide and N,N-dimethylformamide) containing 0.1 M tetra-n-butylammonium perchlorate. The tetrapositively charged compounds are represented by the tetrapyridylporphyrins [TRPyPM] 4+ (X - ) 4 , where R is a methyl or [2-[2-(2-methoxy)ethoxy]ethoxy]ethyl group, M = Mn III I, Mn III Cl, Cu II , or Pd II , and X = I - or Cl - . The tetranegatively charged porphyrins are represented by the tetrasulfonato derivatives [TPPSMn(OAc)] 4- (NH 4 + ) 4 and [TArPSMn(OAc)] 4- (NH 4 + ) 4 , where Ar = 4-O-[2-[2-(2-methoxy)ethoxy]ethoxy]ethylphenyl. Up to seven electrons can be added to the tetrapyridyl porphyrins in three to five reversible reductions, while up to four electrons can be added to the tetrasulfonato derivatives in four reversible processes. Three types of electrochemical behaviors are observed for reduction of the pyridinium groups on the tetrapyridyl porphyrins. One is for the manganese(II) complexes where the four equivalent pyridinium groups are reduced in a single overlapping four-electron-transfer step. Another is for the free-base porphyrin, where four well-separated one-electron reductions occur, while the third is for copper(II) and palladium(II) derivatives, where reduction of the four pyridinium groups proceeds in two well-separated two-electron-transfer steps. The electrochemical and spectroelectrochemical properties were also characterized for a 1:1 mixture of the tetrapositively and tetranegatively charged manganese porphyrins to investigate possible interactions between these two species. An interaction between the two porphyrins was indeed observed in both solvents after electroreduction of the four pyridinium groups, which led to a substantial change in the mechanism for reduction of the pyridinium groups from an initial single overlapping four-electron-reduction process to two well-separated two-electron-transfer processes.

The C3-symmetric cyclotriveratrylene (CTV) was covalently bonded via click chemistry to 1, 2, 3, and 6 zinc(II) porphyrin units to various host for C60. The binding constants, Ka, were measured from the quenching of the porphyrin fluorescence by C60. These constants vary between 400 and 4000 M(-1) and are considered weak. Computer modeling demonstrated that the zinc(II) porphyrin units, [Zn], exhibit a strong tendency to occupy the CTV cavity, hence blocking the access for C60 to land on this site. Instead, the pincer of the type [Zn]----[Zn] and in one case [Zn]----CTV, were found to be the most probable geometry to promote host-guest associations in these systems.

Red (no styryl), green (monostyryl), and blue (distyryl) BODIPY-gallium(III) (BODIPY = boron-dipyrromethene) corrole dyads have been prepared in high yields using click chemistry, and their photophysical properties are reported. An original and efficient control of the direction of the singlet energy transfers is reported, going either from BODIPY to the gallium-corrole units or from gallium-corroles to BODIPY, depending upon the nature of the substitution on BODIPY. In one case (green), both directions are possible. The mechanism for the energy transfers is interpreted by means of through-space Förster resonance energy transfer (FRET).