Effect of the Diamagnetic Single-Crystalline Host on the Angular-Resolved Electron Nuclear Double Resonance Experiments: Case of Paramagnetic [BuN][Cu(opba)] Embedded in Diamagnetic [BuN][Ni(opba)].

The electron spin resonance (ESR) and electron nuclear double resonance (ENDOR) spectroscopies are frequently used to determine hyperfine () and quadrupole () tensors for the paramagnetic transition-metal complexes, which knowledge enables estimation of the spin density distribution in the complex and the assessment of magnetic exchange pathways in polynuclear molecular networks. The most accurate results can be obtained if paramagnetic complexes are isolated in a single-crystalline diamagnetic host. In this work we were able to detect angle-resolved ESR/ENDOR spectra of the paramagnetic [BuN][Cu(opba)] (opba = -phenylenebis(oxamato) complex hosted by the single crystal of diamagnetic [BuN][Ni(opba)], which allow recovery of , , and -tensors, all at once.

Tuning the spin coherence time of Cu(II)-(bis)oxamato and Cu(II)-(bis)oxamidato complexes by advanced ESR pulse protocols.

We have investigated with the pulsed ESR technique at X- and Q-band frequencies the coherence and relaxation of Cu spins = 1/2 in single crystals of diamagnetically diluted mononuclear [-BuN][Cu(opba)] (1%) in the host lattice of [-BuN][Ni(opba)] (99%, opba = -phenylenebis(oxamato)) and of diamagnetically diluted mononuclear [-BuN][Cu(opbo-Pr)] (1%) in the host lattice of [-BuN][Ni(opbo-Pr)] (99%, opbo-Pr = -phenylenebis((propyl)oxamidato)). For that we have measured the electron spin dephasing time at different temperatures with the two-pulse primary echo and with the special Carr-Purcell-Meiboom-Gill (CPMG) multiple microwave pulse sequence. Application of the CPMG protocol has led to a substantial increase of the spin coherence lifetime in both complexes as compared to the primary echo results.