Complexation of free-base and 3d transition metal(II) phthalocyanines with endohedral fullerene Sc3N@C80

Adsorption of lanthanide double-decker phthalocyanines on single-walled carbon nanotubes: structural changes and electronic properties as studied by density functional theory

CONTEXT

Molecular modeling of carbon nanotubes and lanthanide double-decker phthalocyanines hybrids is challenging due to the presence of 4f-electrons. In this paper, we analyzed the trends in structural changes and electronic properties when a lanthanide (La, Gd, and Lu) bisphthalocyanine molecule is adsorbed on the surface of two single-walled carbon nanotubes (SWCNTs) models: armchair and zigzag. The density functional theory (DFT) computations showed that the height of bisphthalocyanines complexes (LnPc₂) when adsorbed on a nanotube (LnPc₂+SWCNT) is the structural feature which is most affected by the nanotube model. The formation energy of the LnPc₂+SWCNT hybrid depends on the metal atom and the nanotube chirality. LaPc₂ and LuPc₂ bind stronger to the zigzag nanotube, while for GdPc₂, bonding to the armchair nanotube is the stronger one. The HOMO-LUMO gap energy (Egap) shows a correlation between the nature of lanthanide and the nanotube chirality. In the case of adsorption on armchair nanotube, E_gap tends to match the gap of isolated LnPc₂, whereas for adsorption on the zigzag nanotube, it is closer to the value for the isolated nanotube model. The spin density is localized on the phthalocyanines ligands (plus on Gd in the case of GdPc₂), when the bisphthalocyanine is adsorbed on the surface of the armchair nanotube. For bonding to zigzag nanotube (ZNT), it extends over both components, except for LaPc₂+ZNT, where spin density is found on the nanotube only.

METHOD

All DFT calculations were carried out using the DMol³ module of Material Studio 8.0 software package from Accelrys Inc. The computational technique chosen was the general gradient approximation functional PBE in combination with a long-range dispersion correction developed by Grimme (PBE-D2), the double numerical basis set DN, and the DFT semi-core pseudopotentials.

H2O·HF@C70: Encapsulation Energetics and Thermodynamics

This report deals with the quantum-chemical evaluation of the energetics and thermodynamics of the simultaneous encapsulation of HF and H2O by the IPR (isolated pentagon rule) C70 fullerene cage, yielding H2O·HF@C70 species which were synthesized and characterized recently, thus further expanding the family of fullerene endohedrals with non-metallic encapsulates. The structures were optimized at the DFT (density functional theory) M06-2X/6-31++G** level. The encapsulation energetics were further refined by the advanced B2PLYPD/6-31++G** and B2PLYPD/6-311++G** methods. After enhancement of the B2PLYPD/6-311++G** encapsulation energy for the BSSE and steric corrections, the encapsulation energy gain was obtained, as 26 kcal/mol. The equilibrium encapsulation thermodynamics were described using the M06-2X/6-31++G** partition functions. The results correspond to our previous evaluations for the water dimer encapsulation by C84 cages.

The donor-acceptor dyad based on high substituted fullero[70]pyrrolidine-coordinated manganese (III) phthalocyanine for photoinduced electron transfer

Donor-acceptor dyads based on manganese porphyrins/phthalocyanines and fullerene derivatives with N-basicity centers have proved as promising photoinduced electron-transfer systems for photovoltaic devices, biologically active compounds, and molecular magnetic materials. The macroheterocyclic chromophore characterized by rich UV-visible-near IR absorption is the basis for the applications above. The problem of the synthesis and the characterization of new effective dyads was solved in this work on the example of the self-organizing system consisting of (octakis-3,5-di-tert-butylphenoxy)phthalocyaninato)manganese(III) acetate, (AcO)MnPc(3,5-di-^tBuPhO)₈, 2',5-di(pyridin-2'-yl)-3,4-fullero[70]pyrrolidine, Py₂C₇₀, and toluene. The phthalocyanine-fullerene dyads in the molecular and cationic form (respectively (AcO)(Py₂C₇₀)MnPc(3,5-di-^tBuPhO)₈ and [(Py₂C₇₀)MnPc(3,5-di-^tBuPhO)₈]⁺(AcO)^-) were observed and described using the chemical kinetics/thermodynamics, UV-vis, IR, ¹H NMR spectroscopy and mass spectrometry methods. The 1: 1 stoichiometry of both dyads was confirmed; the equilibrium and rate constant value, K= (4.86 ± 0.56) × 10⁴ L mol^-1 and k = (4.455 ± 3.37) × 10^-5 s^-1 was observed for the formation of molecular and cationic dyad, respectively. The study of (AcO)MnPc(3,5-di-^tBuPhO)₈ and [(Py₂C₇₀)MnPc(3,5-di-^tBuPhO)₈]⁺AcO^- femtosecond transient absorption spectra points to the photoinduced electron transfer in the dyad, for which the lifetimes and the rate constants of charge separation (τ_CS, k_CS) and charge recombination (τ_CR, k_CR) were defined. The analysis of the relationship of the dyad physicochemical parameters with the molecular structure is represented using previously published data.

Phthalocyanines core-modified by P and S and their complexes with fullerene C60: DFT study

Phthalocyanines (Pcs) and their derivatives have attracted a lot of attention because of their both biological importance and technological applications. The properties of Pcs can be tuned by replacing the central atom, by modifying the periphery of phthalocyanine ring, and by changing the meso-atoms. One more promising pathway for modifying Pcs and their derivatives can be the core-modification, or substitution of the core isoindole nitrogen(s) by other elements. Motivated by the results obtained for some core-modified porphyrins, we investigated computationally complete core-modification of regular Zn phthalocyanine (ZnPc) with P and S. We performed density functional theory studies of the structures, charges, and frontier molecular orbitals of P-core-modified and S-core-modified ZnPcs, ZnPc(P)4 and ZnPc(S)4, using both B3LYP and two dispersion-corrected functionals. Also, we studied computationally formation of complexes between the fullerene C60 and ZnPc(P)4 and ZnPc(S)4. Both ZnPc(P)4 and ZnPc(S)4 show strong bowl-like distortions similar to the results obtained earlier for ZnP(P)4 and ZnP(S)4. The size of the “bowl” cavity of the both core-modified Pcs is essentially the same, showing no dependence on the core-modifying element. For ZnPc(S)4, the HOMO is quite different from those of ZnPc and ZnPc(P)4. When the fullerene C60 forms complexes with the ZnPc(P)4 and ZnPc(S)4 species in the gas phase, it is located relatively far (4.30–5.72 Å) from the one of the P-centers and from the Zn-center of ZnPc(P)4, whereas with ZnPc(S)4 C60 forms relatively short bonds with the Zn-center, varying from ca. 2.0 to ca. 3.0 Å. The very strong deformations of both the ZnPc(P)4 and ZnPc(S)4 structures are observed. The calculated binding energy at the B3LYP/6-31G* level for the C60-ZnPc(P)4 complex is quite low, 1.2 kcal/mol, which agrees with the quite long distances fullerene - ZnPc(P)4, whereas it is noticeably larger, 13.6 kcal/mol, for the C60-ZnPc(S)4 complex which again agrees with the structural features of this complex. The binding energies of the complexes optimized using the dispersion-corrected functionals, CAM-B3LYP and wB97XD, are significantly larger, varying from ca. 14 till 52 kcal/mol which corresponds with the shorter distances between the fullerene and ZnPc(X)4 species.