VOPc maintains an “oxygen-up” orientation and its spin on graphene is S = 1/2: this is an interesting system for qubit applications.

Photoactive organic semiconductor substrates are envisioned as a novel class of bioelectronic devices that transduce light into stimulating biological signals with relevance for retinal implants or guided cellular differentiation. The direct interface between the semiconductor and the electrolyte gives rise to different competing optoelectronic transduction mechanisms. A detailed understanding of such faradaic or capacitive processes and the underlying material science is necessary to develop and optimize future devices. Here, the problem in organic photoelectrodes is addressed based on a planar p‐n junction containing phthalocyanine (H2Pc) and N,N′‐dimethyl perylenetetracarboxylic diimide (PTCDI). The detailed characterization of photoelectrochemical current transients is combined with spectroscopic measurements, impedance spectroscopy, and local photovoltage measurements to establish a model that predicts quantitatively faradaic or capacitive current transients. The decisive elements of the model are the energy levels present at the interface and the voltage building up in the photoelectrode. The result of the efforts is a comprehensive model of photocapacitive and photofaradaic effects that can be applied to developing wireless bioelectronic photostimulation devices.

To improve understanding of M−L bonds in 3d transition metal complexes, analysis by energy decomposition analysis and natural orbital for chemical valence model (EDA‐NOCV) is desirable as it provides a full, quantitative and chemically intuitive ab initio description of the M−L interactions. In this study, a generally applicable fragmentation and computational protocol was established and validated by using octahedral spin crossover (SCO) complexes, as the transition temperature (T1/2) is sensitive to subtle changes in M−L bonding. Specifically, EDA‐NOCV analysis of Fe−N bonds in five [FeII(Lazine)2(NCBH3)2], in both low‐spin (LS) and paramagnetic high‐spin (HS) states led to: 1) development of a general, widely applicable, corrected M+L6 fragmentation, tested against a family of five LS [FeII(Lazine)3](BF4)2 complexes; this confirmed that three Lazine are stronger ligands (ΔEorb,σ+π=−370 kcal mol−1) than 2 Lazine+2 NCBH3 (=−335 kcal mol−1), as observed. 2) Analysis of Fe−L bonding on LS→HS, reveals more ionic (ΔEelstat) and less covalent (ΔEorb) character (ΔEelstat:ΔEorb 55:45 LS→64:36 HS), mostly due to a big drop in σ (ΔEorb,σ ↓50 %; −310→−145 kcal mol−1), and a drop in π contributions (ΔEorb,π ↓90 %; −30→−3 kcal mol−1). 3) Strong correlation of observed T1/2 and ΔEorb,σ+π, for both LS and HS families (R2=0.99 LS, R2=0.95 HS), but no correlation of T1/2 and ΔΔEorb,σ+π(LS‐HS) (R2=0.11). Overall, this study has established and validated an EDA‐NOCV protocol for M−L bonding analysis of any diamagnetic or paramagnetic, homoleptic or heteroleptic, octahedral transition metal complex. This new and widely applicable EDA‐NOCV protocol holds great promise as a predictive tool.