Tuning Up an Electronic Structure of the Subphthalocyanine Derivatives toward Electron-Transfer Process in Noncovalent Complexes with C₆₀ and C₇₀ Fullerenes: Experimental and Theoretical Studies

Abstract

Noncovalent π-π interactions between chloroboron subphthalocyanine (1), 2,3-subnaphthalocyanine (3), 1,4,8,11,15,18-(hexathiophenyl)subphthalocyanine (4), or 4-tert-butylphenoxyboron subphthalocyanine (2) with C and C fullerenes were studied by UV-vis and steady-state fluorescence spectroscopy, as well as mass (APCI, ESI, and CSI) spectrometry. Mass spectrometry experiments were suggestive of relatively weak interaction energies between compounds 1-4 and fullerenes. The formation of a new weak charge-transfer band in the NIR region was observed in solution only for subphthalocyanine 4 when titrated with C and C fullerenes. Molecular structures of the subphthalocyanines 2 and 4 as well as cocrystallite of 4 with C fullerene (4···C) were studied using X-ray crystallography. One of the C fullerenes in the crystal structure of 4···C was found in the concave region between two subphthalocyanine cores, while the other three fullerenes are aligned above individual isoindole fragments of the aromatic subphthalocyanine. The excited-state dynamics in noncovalent assemblies were studied by transient absorption spectroscopy. The time-resolved photophysics data suggest that only electron-rich subphthalocyanine 4 can facilitate an electron-transfer to C or C fullerenes, while no electron-transfer from the photoexcited receptors 1-3 to fullerenes was observed in UV-vis and transient spectroscopy experiments. DFT calculations using the CAM-B3LYP exchange-correlation functional and the 6-31+G(d) basis set allowed an estimation of interaction energies for the noncovalent 1:1 and 1:2 (fullerene:subphthalocyanine) complexes. Theoretical data suggest that the weak (∼3.5-10.5 kcal/mol) van der Waals-type interaction energies tend to increase with an increase of the electron density at the subphthalocyanine core with compound 4 being the best platform for noncovalent interactions with fullerenes. DFT calculations also indicate that 1:2 (fullerene:subphthalocyanine) noncovalent complexes are more stable than the corresponding 1:1 assemblies.

Photoactive preorganized subphthalocyanine-based molecular tweezers for selective complexation of fullerenes

“…Next, fullerene complexation was tested with the different SubPcs. Despite the fact that complexes between fullerenes and electron-rich SubPcs have been previously reported, 5,24 we failed to observe any interactions between monomer-SubPc 4 and C 60 or C 70 under our experimental conditions.k Similarly, no evidence was found for any interactions between dimer-SubPc 2 and C 60 or C 70 . A likely rationale is the electron accepting nature of both dimer-SubPc 2 and fullerenes.k A completely different picture was, however, found when syn-SubPc 1 was titrated with C 60 and C 70 .…”

A computational investigation on core‐expanded subphthalocyanines

“…B3LYP has been proven to be able to reproduce experimental structures accurately . B3LYP density functional, composed of Becke three‐parameter hybrid exchange and Lee‐Yang‐Parr correlation functionals, with 6‐31+G(d) basis sets has been widely used in these subPC derivatives …”

Can MP(P)4 Compounds Form Complexes with C60?

“…We performed the geometry optimizations and frequencies calculations using the Handy and coworkers' long range corrected version of B3LYP, CAM-B3LYP [42] with the split-valence 6-31G* basis set [43,44], further referred to as CAM-B3LYP/6-31G*. So far, different theoretical approaches have been used to study the complexes between porphyrins and their derivatives and fullerenes, for example: pure generalized gradient approximation (GGA) functional PBE, global hybrid meta-GGA functional M06, hybrid functional B3LYP, and wB97XD hybrid density functional including empirical atomic-pairwise dispersion corrections following the Grimme's D2 dispersion scheme (D) by Baruah and co-workers in the studies of systems based on fullerene/graphene oxide and porphyrin/smaragdyrin [33]; hybrid functional B3LYP in the recent study of noncovalent interactions between C 60 -dipyridyl and zinc porphyrin dimer by Stangel et al [45]; B97-D3 functional including dispersion corrections in the study of supramolecular ensembles of conjugated porphyrin dimers with C 60 by Moreira et al [32]; PBE with included semi-empirical 'DFT+D3' term in the studies of fullerene-porphyrin supramolecular nanocables by Buldum and Reneker [31]; CAM-B3LYP along with wB97XD, TPSSh, M06, and M06L functionals in the studies of Rhoda et al on noncovalent complexes of subphthalocyanine derivatives with C 60 and C 70 fullerenes [46]. We decided to choose the CAM-B3LYP approach because of its superiority over the standard "pure" and "hybrid" exchange-correlation functionals in treating noncovalent weak long-distance interactions which should take place in the studied complexes.…”