• Energy Research

AbstractWe describe the synthesis of a series of phthalocyanine (Pc)–perylenediimide (PDI)8 “octad” molecules, in which eight PDI moieties are attached to a Pc core through alkyl‐chain linkers. There is clear spectroscopic evidence that these octads can exist as non‐aggregated “monomers” or form aggregates along the Pc cores, depending on the type of Pc and the solvent medium. In the low dielectric constant solvents, into which the octads are soluble, photoexcitation of the PDI units leads to rapid energy transfer to the Pc centre, rather than a charge separation between moieties. In octad monomers, the Pc singlet excited‐state decays within tens of ps, whereas the excitons are stabilised in the aggregated form of the molecules, typically with lifetimes in the order of 1–10 ns. By contrast, in an octad design in which π–π interactions are suppressed by the steric hindrance of a corona of incompatible glycol tails around the molecule, a more straightforward photophysical interaction of Förster energy transfer between the PDI moieties and Pc core may be inferred. We consider these molecules as prototypical multichromophoric aggregates, giving delocalised states with considerable flexibility of design.

In Germany, there are over 32,000 schools, representing great potential for climate protection. On the one hand, this applies to educational work, as understanding the effects of climate change and measures to reduce GHG emissions is an important step to empower students with knowledge and skills. On the other hand, school buildings are often in bad condition, energy is wasted, and the possibilities for using renewable energies are hardly used. In our “Schools4Future” project, we enabled students and teachers to draw up their own CO2 balances, identify weaknesses in the building, detect wasted electricity, and determine the potential for using renewable energies. Emissions from the school cafeteria, school trips, and paper consumption could also be identified. The fact that the data can be collected by the students themselves provides increased awareness of the contribution made to the climate balance by the various school areas. The most climate-friendly school emits 297 kg whilst the school with the highest emissions emits over one ton CO2 per student and year. Our approach is suitable to qualify students in the sense of citizen science, carry out a scientific investigation, experience self-efficacy through one’s own actions, and engage politically regarding their concerns.

We report on the synthesis and detailed photo-physical investigation of four model chromophore side chain polyisocyanopeptides: two homopolymers of platinum-porphyrin functionalized polyisocyanopeptides (Pt-porphyrin-PIC) and perylene-bis(dicarboximide) functionalized polyisocyanopeptides (PDI-PIC), and two statistical copolymers with different ratios of Pt-porphyrin and PDI molecules attached to a rigid, helical polyisocyanopeptide backbone. (1)H NMR and circular dichroism measurements confirm that our model compounds retain a chiral architecture in the presence of the chromophores. The combination of Pt-porphyrin and PDI chromophores allows charge- and/or energy transfer to happen. We observe the excitation and relaxation pathways for selective excitation of the Pt-porphyrin and PDI chromophores. Studies of photoluminescence and transient absorption on nanosecond and picosecond scales upon excitation of Pt-porphyrin chromophores in our multichromophoric assemblies show similar photophysical features to those of the Pt-porphyrin monomers. In contrast, excitation of perylene chromophores results in a series of energy and charge transfer processes with the Pt-porphyrin group and forms additional charge-transfer states, which behave as an intermediate state that facilitates electronic coupling in these multichromophoric systems.

Schools play an important role in achieving climate protection goals, because they lay the foundation of knowledge for a responsible next generation. Therefore, schools as institutions have a special role model function. Enabling schools to become aware of their own carbon footprint (CF) is an important prerequisite for being able to tap the substantial CO2 reduction potential. Aiming at the direct involvement of students in the assessment process, a new assessment tool was developed within the Schools4Future project that gives students the opportunity to determine their own school’s CF. With this instrument the CO2 emissions caused by mobility, heating and electricity consumption as well as for food in the school canteen and for consumables (paper) can be recorded. It also takes into account existing renewable energy sources. Through the development of the tool, not only a monitoring instrument was established but also a concrete starting point from which students could take actions to reduce Greenhouse Gas (GHG) emissions. This paper presents the tool and its methods used to calculate the CF and compares it with existing approaches. A comparative case study of four pilot schools in Germany demonstrates the practicability of the tool and reveals fundamental differences between the GHG emissions.