Nanoscale Visualization of Photodegradation Dynamics of MAPbI3 Perovskite Films.

Herein, we report the nanoscale visualization of the photochemical degradation dynamics of MAPbI3 (MA = CH3NH3+) using infrared scattering scanning near-field microscopy (IR s-SNOM) combined with a series of complementary analytical techniques such as UV-vis and FTIR-spectroscopy, XRD, and XPS. Light exposure of the MAPbI3 films resulted in a gradual loss of MA+ cations starting from the grain boundaries at the film surface and slowly progressing toward the center of the grains and deeper into the bulk perovskite phase. The binary lead iodide PbI2 was found to be the major perovskite photochemical degradation product under the experimental conditions used. Interestingly, the formation of the PbI2 skin over the perovskite grains resulted in a largely enhanced photoluminescence, which resembles the effects observed for core-shell quantum dots. The obtained results demonstrate that IR s-SNOM represents a powerful technique for studying the spatially resolved degradation dynamics of perovskite absorbers and revealing the associated material aging pathways.

Cleavage of the C-H Bond in Bu3MeP+ by Zinc Porphyrin Dianions: Formation of {ZnII(CH2PBu3)(TPyPH)}- Containing Zn-C(ylide) Bond and the (TPyPH)3- Macrocycle Showing Strong NIR Absorption.

Reduction of {ZnII(TPyP)} to the {ZnII(TPyP)}2- dianions (TPyP: tetra(4-pyridyl)porphyrin) in the presence of Bu3MeP+ allows one to observe the C-H bond cleavage in the methyl group of Bu3MeP+ to form (Bu3MeP+){ZnII(CH2PBu3)(TPyPH)}-·0.337C6H5CH3 (1). Salt 1 is the first coordination complex of neutral CH2PBu3 ylide and metalloporphyrin. The released hydrogen atom attacks the meso-carbon atom of TPyP4- forming a TPyPH3- macrocycle related to phlorins. Decreased symmetry of the TPyPH3- allows the observation of a strong NIR absorption. We discuss the molecular structure, optical, and magnetic properties of 1 together with its formation pathways.

Dianionic Titanyl and Vanadyl (Cation+ )2 [MIV O(Pc4- )]2- Phthalocyanine Salts Containing Pc4- Macrocycles.

In this study, the titanyl and vanadyl phthalocyanine (Pc) salts (Bu4 N+ )2 [MIV O(Pc4- )]2- (M=Ti, V) and (Bu3 MeP+ )2 [MIV O(Pc4- )]2- (M=Ti, V) with [MIV O(Pc4- )]2- dianions were synthesized and characterized. Reduction of MIV O(Pc2- ) carried out with an excess of sodium fluorenone ketyl in the presence of Bu4 N+ or Bu3 MeP+ is exclusive to the phthalocyanine centers, forming Pc4- species. During reduction, the metal +4 charge did not change, implying that Pc is an non-innocent ligand. The Pc negative charge increase caused the C-N(pyr) bonds to elongate and the C-N(imine) bonds to alternate, thus increasing the distortion of Pc. Jahn-Teller effects are significant in the [eg(π*)]2 dianion ground state and can additionally distort the Pc macrocycles. Blueshifts of the Soret and Q-bands were observed in the UV/Vis/NIR when MIV O(Pc2- ) was reduced to [MIV O(Pc.3- )].- and [MIV O(Pc4- )]2- . From magnetic measurements, [TiIV O(Pc4- )]2- was found to be diamagnetic and (Bu4 N+ )2 [VIV O(Pc4- )]2- and (Bu3 MeP+ )2 [VIV O(Pc4- )]2- were found to have magnetic moments of 1.72-1.78 µB corresponding to an S=1/2 spin state owing to VIV electron spin. As a result, two latter salts show EPR signals with VIV hyperfine coupling.

The Salts of Copper Octafluoro- and Hexadecafluorophthalocyanines Containing [CuII(F8Pc)4-]2- Dianions and [CuF16Pc]- Monoanions.

Crystalline anionic salts with copper octafluoro- and hexadecafluorophthalocyanines, (Bu4N+)2[CuII(F8Pc)4-]2-·2C6H4Cl2 (1) and (PPN+)3[CuF16Pc]33-·2C6H5CN (2), where PPN+ is bis(triphenylphosphoranylidene)ammonium and Pc is phthalocyanine, have been obtained. The absence of noticeable absorption in the NIR range and DFT calculations for 1 indicate that both negative charges are mainly localized on the Pc ligand, and that the [CuII(F8Pc)4-]2- dianions are formed without reduction of CuII. The magnetic moment of 1.60 µB corresponds to the contribution of one S = 1/2 spin per dianion. The spin is localized on the CuII atom, which shows an EPR signal characteristic of CuII. Dianions are isolated in 1, providing only weak magnetic coupling of spins with a Weiss temperature of -4 K. Salt 2 contains closely packed π-π stacks built of [CuF16Pc]- anions of types I and II, and the interplanar distances are 3.187 and 3.275 Å. According to the DFT calculations, the [CuF16Pc]- anions of types I and II can have different charge distributions, with localization of an extra electron on the copper atoms to form diamagnetic [CuI(F16Pc)2-]- monoanions or delocalization of an extra electron on the F16Pc ligand to form [CuII(F16Pc)•3-]•- having an S = 1/2 (CuII) + 1/2 (F16Pc•3-) spin state. In fact, at 300 K, the magnetic moment of 2 of 3.25 µB per formula unit is rather close to the contribution from two [CuII(F16Pc)•3-]•- (calculated µeff is 3.46 µB). The Weiss temperature of -21.5 K indicates antiferromagnetic coupling of spins, which can be modeled by stronger intermolecular coupling between (F16Pc)•3- with J1/kB = -23.5 K and weaker intramolecular coupling between CuII and (F16Pc)•3- with J2/kB = -8.1 K. This interaction is realized in the {[CuII(F16Pc)•3-]•-}2 dimers separated by diamagnetic [CuI(F16Pc)2-]- species. In spite of the stacking arrangement of phthalocyanine macrocycles in 2, the inhomogeneous charge distribution and nonuniform distances between the macrocycles should suppress electrical conductivity.

Synthesis and structure of multicomponent crystals of fullerenes and metal tetraarylporphyrins.

The preparation of fullerene complexes with metal tetraarylporphyrins in the presence of excess ferrocene (Cp(2)Fe) results in the formation of new solvent-free and multicomponent molecular crystals. New isomorphous complexes of C(60) with PyZnTPP (ZnTPP identical with zinc 5,10,15,20-tetraphenyl-21H,23H-porphyrinate) and PyCoTPP (CoTPP identical with cobalt(II) 5,10,15,20-tetraphenyl-21H,23H-porphyrinate) containing Cp(2)Fe and the isostructural C(70) complex with PyZnTPP have been prepared. The crystal structures of the new layered C(60) complexes CoTMPP x C(60) (obtained in the presence of Cp(2)Fe) and CoTMPP x 2C(60) x 3C(7)H(8) (obtained in the absence of Cp(2)Fe) have been described (CoTMPP identical with cobalt(II) 5,10,15,20-tetrakis(p-methoxyphenyl)-21H,23H-porphyrinate). Cobalt atoms of the PyCoTPP and CoTMPP molecules are weakly coordinated to C(60) with Co...C(C(60)) distances in the 2.64-2.82 A range, whereas zinc atoms of PyZnTPP, as well as cobalt atoms of the CoTMPP molecules in the solvent-free phase, form only van der Waals contacts with fullerenes. Different packing arrangements in the crystals of fullerene-porphyrin complexes have been discussed.