Improved photodecarboxylation properties in zinc photocages constructed using m-nitrophenylacetic acid variants

The methoxy- and fluoro-derivatives of meta-nitrophenylacetic acid (mNPA) chromophores undergo photodecarboxylation with comparable quantum yields to unsubstituted mNPA, but uncage at red-shifted excitation wavelengths. This observation prompted us to investigate DPAdeCageOMe (2-[bis(pyridin-2-ylmethyl)amino]-2-(4-methoxy-3-nitrophenyl)acetic acid) and DPAdeCageF (2-[bis(pyridin-2-ylmethyl)amino]-2-(4-fluoro-3-nitrophenyl)acetic acid) as Zn2+ photocages. DPAdeCageOMe has a high quantum yield and exhibits other photophysical properties comparable to XDPAdeCage ({bis[(2-pyridyl)methyl]amino}(9-oxo-2-xanthenyl) acetic acid), the best perforiming Zn2+ photocage reported to date. Since the synthesis of DPAdeCageOMe is more straightforward than XDPACage, the new photocage will be a highly competitive tool for biological applications.

Catalytic Asymmetric Fluorination of Alkyl 1-indanone-2-carboxylates Ruled by Pybox-Eu(III) Combination

A highly enantioselective catalytic method for the synthesis of quaternary α-fluoro derivatives of 3-oxo esters is described. The reaction uses europium (III) triflate and commercially available chiral pybox-type C2-symmetric ligand. Excellent results in terms of yields and enantioselectivities were assured using the electrophilic NFSI reagent under mild reaction conditions.

Aryl-Substituted Boron Subphthalocyanines and their Application in Organic Photovoltaics

A family of five axial aryl-substituted boron subphthalocyanine (BsubPc) derivatives bearing a hydrido, methyl, methoxy, phenyl, or fluoro substituent at the para position of the aryl were synthesised from Br-BsubPc and the corresponding aryl Grignard reagent in moderate yields. The physicochemical characterisation of these derivatives gave similar absorption, photoluminescence, and cyclic voltammetry profiles and photoluminescence quantum yields, indicating that the nature of the substituent at the para position does not influence the basic photophysical properties of this generic class of BsubPcs. Conversely, the solid-state structural arrangement obtained from single crystals is highly dependent on the para substituent; for the non-polar hydrido, methyl, and phenyl substituents, only concave isoindole π interactions are present. Substitution for the polar methoxy or fluoro ligand affords one-dimensional ribbons formed by convex π interactions, where these ribbons further interact through concave isoindole π interactions with the adjacent ribbon, creating an extended two-dimensional π network. On incorporation of the hydrido, methyl, and fluoro derivatives into organic photovoltaic (OPV) devices, similar results and device metrics were obtained with the methyl and fluoro derivatives. Both, however, were significantly outperformed by the hydrido derivative. The uniqueness of the hydrido derivative is only realised once incorporated into OPVs as it shares the same basic physical properties as the other derivatives. Given these findings, we identify the hydrido derivative as the aryl-BsubPc with the most promise for future work in OPVs.

Description of Bond Pseudorotation, Bond Pseudolibration, and Ring Pseudoinversion Processes Caused by the Pseudo-Jahn–Teller Effect: Fluoro Derivatives of the Cyclopropane Radical Cation

Curvilinear coordinates are used to describe the molecular geometry and the pseudo-Jahn–Teller surface of F-substituted cyclopropane radical cations using the equation-of-motion coupled cluster EOMIP-CCSD/cc-pVTZ approach. The monofluoro derivative 2 undergoes bond pseudolibration (incomplete bond pseudorotation) between two symmetry-equivalent biradicaloid forms separated by a barrier of 2.2 kcal mol–1 (1 kcal mol–1 = 4.186 kJ mol–1) at low temperature. Bond pseudorotation and ring pseudoinversion have barriers of 12.1 and 16.5 kcal mol–1 respectively. The relative energies of 2 are affected by the distribution of the positive charge in the C3 ring and the formation of a CF bond with partial π character. There is a change of the CF bond length from 1.285 to 1.338 Å along the bond pseudorotation path. The changes of the CF bond outweigh the deformation effects of the C3 ring; however, both are a result of the pseudo-Jahn–Teller effect according to an (A′ + A′′) ⊗ (a′ + a′′) interaction. For the pentafluoro derivative 3 of the cyclopropane radical cation, bond pseudorotation has a barrier of 16.3 kcal mol–1 whereas ring pseudoinversion is hindered by a barrier of 21.7 kcal mol–1. Radical cation 3 is the first example of a trimethylene radical cation.