Two-dimensional (2D) organic-inorganic perovskites have rapidly become an attractive alternative to traditional three-dimensional (3D) perovskite solar-cell absorbers owing to their improved stability and processability. Despite their advantages, the insulating nature of the organic cations and diminished light absorption limit their overall performance. Herein, it is demonstrated that the incorporation of conjugated diynes in hybrid 2D perovskites, and subsequent thermal treatment results in the formation of 2D perovskites that incorporate polydiacetylenes in their structure. Furthermore, it is shown that oxygen or iodine doping results in the formation of stable radicals within the material alongside a drastic shift of the band gap from 3.0 to 1.4 eV and in-plane conductivity improvements of up to three orders of magnitude, which lead to record conductivities for 2D halide perovskites (n=1).

Simple acid–base properties explain the differences in amide and imide dimerisation, and represent an alternative to the secondary interactions hypothesis.

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Redefining interactions: The concept of the resonance-impaired hydrogen bond (RIHB) as an interaction in which a conjugated π system strongly impairs the formation of a hydrogen bond (HB) is introduced. A typical HB involving charged species can have a formation energy of tens of kcal mol , whereas the corresponding value for the examined RIHB is only 2.6 kcal mol . Quantum chemical topology tools are used to analyse the low formation energy of the studied RIHBs.

State-of-the-art chemical bonding analyses show that water clusters have a bifunctional catalytic role in the formation of HSO in acid rain. The embedded HO monomers mitigate the change in the chemical bonding scenario of the rate-limiting step, reducing thereby the corresponding activation energy in accordance with Hammond's postulate. We expect that the insights given herein will prove useful in the elucidation of the catalytic mechanisms of water in inorganic and organic aqueous chemistry.

Thioureas are an important scaffold in organocatalysis because of their ability to form hydrogen bonds that activate substrates and fix them in a defined position, which allows a given reaction to occur. Structures that enhance the acidity of the thiourea are usually used to increase the hydrogen-bonding properties, such as 3,5-bis(trifluoromethyl)phenyl and boronate ureas. Herein, we report the synthesis of bifunctional thioureas with a chiral moiety that include either a trifluoromethyl or methyl group. Their catalytic performance in representative Michael addition reactions was used in an effort to compare the electronic effects of the fluorination at the methyl group. The observed differences concerning yields and ee values cannot be attributed solely to the different steric environments; theoretical results indicate distinct interactions within the corresponding transition states. The calculated transition states show that the fluorinated catalysts have stronger N-H···O and C-H···F hydrogen bonds, while the nonfluorinated systems have C-H···π contacts. These results have shown that a variety of hydrogen-bonding interactions are important in determining the yield and selectivity of thiourea organocatalysis. These details can be further exploited in catalyst design.

Tw o-dimensional (2D) organic-inorganic perovskites have rapidly become an attractive alternative to traditional three-dimensional (3D) perovskite solar-cell absorbers owingt ot heir improved stability and processability.D espite their advantages,t he insulating nature of the organic cations and diminished light absorption limit their overall performance.H erein, it is demonstrated that the incorporation of conjugated diynes in hybrid 2D perovskites,a nd subsequent thermal treatment results in the formation of 2D perovskites that incorporate polydiacetylenes in their structure.F urthermore,i ti ss hown that oxygen or iodine doping results in the formation of stable radicals within the material alongside adrastic shift of the band gap from 3.0 to 1.4 eV and in-plane conductivity improvements of up to three orders of magnitude, which lead to recordc onductivities for 2D halide perovskites (n = 1). Two-dimensional (2D) organic-inorganic hybrid perovskiteshave recently attracted attention as viable alternatives to three-dimensional (3D) perovskites solar cells absorbers such as MAPbI 3 (MA = methylammonium) and related materials. Compared to the 3D analogues,2 Dp erovskites have shown improved processability and stability towards water and light. [1][2][3][4][5][6] This can be easily rationalized when considering the hydrophobic nature of the cations that replace the volatile and hydrophilic methylammonium. [1][2][3][4][5] Thei nsulating nature of the organic cations in 2D perovskites also disrupts the electronic structure of these materials,w hich leads to diminished light absorption (larger band gaps) and conductivities.T his peculiar electronic structure,w hich consists of alternating semiconducting and insulating layers,h as been described as aq uantum-well structure. [7][8][9] In this work, we describe how the incorporation of conjugated diynes into 2D lead halide perovskites and subsequent thermal treatment results in the topochemical formation of 2D lead halide perovskites that incorporate polydiacetylenes into their structure.F urthermore,w es how that by oxygen or iodine doping we can generate additional carriers that generate important changes in the properties of these materials, shifting the optical band gap from 3.0 to 1.4 eV and improving the conductivity by up to three orders of magnitude, effectively inverting the traditional quantum-well structure (Figure 1a,b).Seminal work by Tieke and collaborators [10][11][12][13] showed that irradiating 2D perovskites with unsaturated organic cations resulted in the topochemical polymerization of such cations with retention of the 2D hybrid perovskite structure.M ost studies by Tieke however,f ocused on the use of cadmium chloride layers and diene monomers,w hich have large band gaps and form polymers without notable electronic properties.L ater, Takeoka and co-workers incorporated polydiacetylenes in lead halide perovskites;however, they used gamma radiation to induce polymerization, which makes this technique unpractical for most applications. [14] Other attemp...

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