Probing the interplay between lattice dynamics and short-range magnetic correlations in CuGeO3 with femtosecond RIXS

Investigations of magnetically ordered phases on the femtosecond timescale have provided significant insights into the influence of charge and lattice degrees of freedom on the magnetic sub-system. However, short-range magnetic correlations occurring in the absence of long-range order, for example in spin-frustrated systems, are inaccessible to many ultrafast techniques. Here, we show how time-resolved resonant inelastic X-ray scattering (trRIXS) is capable of probing such short-ranged magnetic dynamics in a charge-transfer insulator through the detection of a Zhang–Rice singlet exciton. Utilizing trRIXS measurements at the O K-edge, and in combination with model calculations, we probe the short-range spin correlations in the frustrated spin chain material CuGeO3 following photo-excitation, revealing a strong coupling between the local lattice and spin sub-systems.

Cis and trans linkage of spin frustrated copper triangles creating Cu6 clusters

Two C3-symmetric guanidine-based copper triangles bridged by acetates in a cis manner and by chloride anions in a trans manner, respectively gave rise to two antiferromagnetically coupled hexanuclear CuII compounds, namely [Cu6L2Cl(μ-OAc)(DMF)3]·DMF (Cu6) and [Cu6L2(μ-Cl)2(DMF)4] (Cu6Cl)(where L stands for fully deprotonated tris (2-hydroxybenzylidene) triaminoguanidinium chloride, H5L). The experimental magnetic data of the two compounds were analyzed theoretically. A relatively good agreement with the experimental data was obtained when using the wavefunction theory (CASSCF) in combination with DFT (B3LYP) calculations for the very strong antiferromagnetic coupling within the Cu3 triangles (Javg = − 300 cm−1 for Cu6 and Javg = − 250 cm−1 for Cu6Cl), leading to spin-frustrated systems. It is worth mentioning that the electronic structure of each CuII center remains very similar in each complex with a Kramers ground state well separated from the first excited state (over 12000 cm−1) and weakly anisotropic (g∥ ≈ 2.40 and g⊥ ≈ 2.10).

Tuning Activity and Selectivity During Alkyne Activation by Gold(I)/Platinum(0) Frustrated Lewis Pairs

Introducing transition metals into frustrated Lewis pair systems has attracted considerable attention in recent years. Here we report a selection of three metal-only frustrated systems based on Au(I)/Pt(0) combinations and their reactivity towards alkynes. We have inspected the activation of the simplest alkyne, namely acetylene, as well as of other internal and terminal triply bonded hydrocarbons. The gold(I) fragments are stabilized by three bulky phosphines bearing terphenyl groups. We have observed that subtle modifications on the substituents of these ligands proved critical to control the regioselectivity of acetylene activation and the product distribution resulting from C(sp)—H cleavage of phenylacetylene. A mechanistic picture based on experimental observations and computational analysis is provided. As a result of the cooperative action of the two metals of the frustrated pairs, several uncommon heterobimetallic structures have been fully characterized.

Tuning Activity and Selectivity During Alkyne Activation by Gold(I)/Platinum(0) Frustrated Lewis Pairs

Introducing transition metals into frustrated Lewis pair systems has attracted considerable attention in recent years. Here we report a selection of three metal-only frustrated systems based on Au(I)/Pt(0) combinations and their reactivity towards alkynes. We have inspected the activation of the simplest alkyne, namely acetylene, as well as of other internal and terminal triply bonded hydrocarbons. The gold(I) fragments are stabilized by three bulky phosphines bearing terphenyl groups. We have observed that subtle modifications on the substituents of these ligands proved critical to control the regioselectivity of acetylene activation and the product distribution resulting from C(sp)—H cleavage of phenylacetylene. A mechanistic picture based on experimental observations and computational analysis is provided. As a result of the cooperative action of the two metals of the frustrated pairs, several uncommon heterobimetallic structures have been fully characterized.

Tuning Activity and Selectivity During Alkyne Activation by Gold(I)/Platinum(0) Frustrated Lewis Pairs

Introducing transition metals into frustrated Lewis pair systems has attracted considerable attention in recent years. Here we report a selection of three metal-only frustrated systems based on Au(I)/Pt(0) combinations and their reactivity towards alkynes. We have inspected the activation of the simplest alkyne, namely acetylene, as well as of other internal and terminal triply bonded hydrocarbons. The gold(I) fragments are stabilized by three bulky phosphines bearing terphenyl groups. We have observed that subtle modifications on the substituents of these ligands proved critical to control the regioselectivity of acetylene activation and the product distribution resulting from C(sp)—H cleavage of phenylacetylene. A mechanistic picture based on experimental observations and computational analysis is provided. As a result of the cooperative action of the two metals of the frustrated pairs, several uncommon heterobimetallic structures have been fully characterized.