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The Faraday Discussion 'From optical to THz control of materials' was held in London, UK, and online on the 23rd, 24th, and 25th May 2022. The meeting brought together established and early-career scientists, postgraduate students, scientific editors, and industrial researchers in the field of spectroscopy and materials science from over ten different countries interested in exploring the physical properties of materials at ultrafast timescales driven by optical and THz excitations. This conference report provides highlights of this meeting and we give summaries of the presentations including the introductory lecture, all the papers discussed, and the concluding remarks. [ABSTRACT FROM AUTHOR]

In this work we report a new PbII coordination polymer [Pb3L2(N3)4] n , which was obtained from Pb(N3)2 and 1-(pyridin-2-yl)ethylidenepicolinohydrazide (HL). The complex exhibits a 1D polymeric chain, constructed from the {[Pb3(N3)4]2+}n backbone, decorated with deprotonated organic L− ligands. The latter ligands are pentadentate and link two metal cations. The PbII ions were found to be in a N5O or N5O2 coordination environment, formed by covalent bonds. The azide ligands either bind four metals in a μ4-1,1,3,3 coordination mode or are coordinated to metal centers as terminal ligands. All the metal centers exhibit a hemidirected coordination geometry with a pronounced coordination gap, which allows the close approach of an additional nitrogen atom arising from an adjacent terminal azide ligand. A simplified underlying network of [Pb3L2(N3)4] n , without considering Pb⋯N tetrel bonds, exhibits the tetranodal 3,4,4,4-connected chain topology, while considering all Pb⋯N tetrel bonds, the binodal 4,5-connected chain topology was shown. The crystal packing of [Pb3L2(N3)4] n is reinforced by intermolecular π⋯π stacking interactions, formed by PbII-based five-membered chelate metallocycles and pyridine rings. In-depth bonding analysis using ETS-NOCV, IQA and NCI methods demonstrates that although the azide anions experience significant steric crowding due to repulsive azide–azide interactions, they are engaged in strong attractive, Coulomb dominated, dative-covalent Pb–N and tetrel-type Pb⋯N connections, which are further augmented by weak exchange–correlation driven C–H⋯N hydrogen bonds as well as London dispersion forces due to metallocycle units. The diffuse reflectance spectrum of [Pb3L2(N3)4] n revealed a broad band with two maxima in the UV region, corresponding to intraligand transitions, and an intense shoulder in the visible region, corresponding to metal-to-ligand charge-transfer. The latter shoulder explains the observed yellow colour of the complex. [ABSTRACT FROM AUTHOR]

Three cadmium(II) coordination polymers, namely {[Cd(HLI)(NO3)2]·0.5MeOH}n (1), {[Cd(HLII)(NO3)2]·EtOH}n (2), and [Cd2(LII)2(NO3)2]n (3), have been self-assembled from Cd(NO3)2 and N,N′,O-pincer-type isonicotinoylhydrazone-based ditopic ligands (HLI = N′-(pyridin-2-ylmethylene)isonicotinohydrazide and HLII = N′-(1-(pyridin-2-yl)ethylidene)isonicotinohydrazide) and have been characterized experimentally and by DFT computations. In compounds 1 and 2, the corresponding ligand is coordinated to the metal center in the keto form and acted as a tetradentate chelating–bridging agent in which the nitrogen atom of the 4-pyridine ring is coordinated to the cadmium center of the neighboring unit, yielding 1D zig-zag coordination polymers. In compound 3, the ligand was singly-deprotonated and is coordinated in the enolic form with the nitrate ion further acted as a bridging agent, yielding a 2D network. It is revealed by the extended transition state natural orbital for chemical valence (ETS-NOCV) charge and energy decomposition scheme that typical hydrogen bonds O–H⋯O and N–H⋯O, which constitute the networks of 1 and 2, though dominated by a classic Coulomb term, are characterized by an equally important London dispersion constituent due to extra π⋯π and C–H⋯X contacts (X = O, H–C, H–N). The architecture of 3 is due to ionic and dative-covalent Cd–X (X = N, O) bonds as well as London dispersion-driven homopolar dihydrogen C–H⋯H–C and C–H⋯O interactions. NOCV-based representation allowed us to determine that hydrogen bonds O–H⋯O are twice weaker than the corresponding N–H⋯O in the networks of 1 and 2. [ABSTRACT FROM AUTHOR]

We report the design, structural, spectroscopic and computational characterization of the two new quasiaromatic Möbius chelate coordination compounds fabricated from Cd(NO3)2·4H2O and a bulky helical organic ligand derived from benzildihydrazone and 2-pyridinecarboxaldehyde (L) in the presence and absence of two equivalents of NaNO2, namely [Cd(NO2)x(NO3)2-x(L)]·2MeOH (1·2MeOH) and [Cd(NO3)2(L)]·MeOH (2·MeOH). The former complex was found to extensively lose one of the lattice solvent molecules of methanol under ambient conditions upon isolation from the mother liquor. Therefore, the crystal structure of 1·2MeOH was obtained at 100 K, namely [Cd(NO2)1.67(NO3)0.33(L)]·2MeOH ((1-100 K)·2MeOH), and at 296 K, namely [Cd(NO2)1.57(NO3)0.43(L)]·2MeOH ((1-296 K)·MeOH). In all the structures, anions exhibit a chelate 2-O,O-mode. It was found that the reported Cd-NO2 and Cd-NO3 connections are largely ionic in nature, followed by dative covalent charge delocalization and the London dispersion constituents. The electron density of delocalized bonds (EDDB) function and the extended transition state (ETS) energy decomposition method combined with the natural orbitals for chemical valence (ETS-NOCV) have shown sizeable p-delocalizations within the twisted ligand L suggesting quasi-aromatic Möbius features of the Cd-L chelate. Finally, the optical properties of (1-296 K)·MeOH and 2·MeOH have been investigated by diffuse reflectance spectroscopy. [ABSTRACT FROM AUTHOR]

The perfluorinated alkoxy silanes {(F3C)3CO}3SiH (1) and {(F5C6)3CO}2Si(Cl)H (2) were prepared and fully characterized. Despite the high calculated Brønsted acidities, all attempts to deprotonate 1 and 2 to give the conjugate silanide ions failed due to the exceptionally short and strong Si–H bonds. In the solid state, the Si–H units are not involved in any intermolecular interactions, but instead the crystal packing consists of exceptionally short and strong F⋯F interactions. The cohesive energies are entirely comprised of London dispersion interactions, similarly as in the crystal structures of noble gases. [ABSTRACT FROM AUTHOR]

In this article, we present a summary of the Faraday Discussion that took place on September 21–23, 2022 in London, UK. The primary goal of this event was to promote and discuss the recent developments in the field of nanoalloys. Here we briefly outline each scientific session as well as other conference events. [ABSTRACT FROM AUTHOR]