Excited‐State Dynamics of Metal String Complex Ni₃(dpa)₄X₂ from Femtosecond Transient Absorption Spectra

Abstract

The excited-state dynamics of Ni(3)(dpa)(4)X(2), in which dpa is the ligand di(2-pyridyl)amido and X = NCS or Cl, are investigated by transient absorption spectroscopy. The pi pi* and dd states are excited upon irradiation at wavelengths of 330 and 600 nm, respectively. Similar transient spectra are observed under the experimental temporal resolution. The transient species also show weak absorption. It is proposed that a low-lying metal-centered dd state is accessed immediately after excitation. Analyses of the experimental kinetic traces reveal a rapid conversion from a ligand-centered pi pi* state to a metal-centered dd state in 0.1-0.4 ps. Vibrational cooling occurs with a time coefficient of 3.0-15.9 ps. From the spectral shift observed in the transient spectra relative to the steady-state spectra, the dd state is assigned as B(1)/B(2)(Ni(t)). This dd state eventually converts to the electronic ground state, in about 100 ps for the isothiocyanate complex and 200 ps for the chloride. In this trimetal string complex, relaxation to the ground electronic surface after excitation is therefore rapid.

Study of Electronic and Vibrational Structures of Reduced, Neutral, and Oxidized Ni3(dpa)4X2 Using Density Functional Theory and Raman Spectroscopy

“…Figure S1 shows the hole–electron distributions of these S13 and S21 transitions. Bands of less than 400 nm corresponded to the π–π* of the equatorial ligands, which confirmed the experimental assignments of Cheng et al in that excitation in the ultraviolet and visible bands accessed the ligand and metal moieties, separately Table lists the experimental and calculated electronic bands and their assignments.…”

“…The band characters analyzed by the IFCT method for each excited transition are listed in Table S1. Most vertical transitions with oscillator strengths were from the equatorial ligands and/or the metal ions rather than the axial ligands, resulting in similar visible absorption spectra of complexes with various axial ligands . The band at 630 nm (607 nm cal.)…”

Charge and Energy Transfer Dynamics in Dimethylsilylene-Spaced Aminostyrene Stilbene Monomer Using Time-Resolved Techniques

“…The details of the setup are described elsewhere. 10 The samples were excited at wavelength 266 nm; this light source was generated by tripling the output from a femtosecond laser (Hurricane, Spectra Physics, 800 nm, 1 kHz, 1 mJ/pulse, and 100 fs). The probe beam white light continuum was generated by focusing the fundamental output 800 nm on a 3-mm-thick water cell (range 440−670 nm).…”

New trinuclear metal string complexes containing rigid Hdzp ligands: synthesis, structure, magnetism and DFT calculation (Hdzp = 1,9-diazaphenoxazine)

“…18 The Ni-Ni bond distances in 2 are ∼2.48 Å, which are 0.05 Å longer than those in [Ni 3 (dpa) 4 (NCS) 2 ] (5). 19 Since the rigidity of the dzp − ligand resulting from the C-O-C bonds may increase the strain of the bite angle (Fig. 1, N1-N2-N3), it may also lead to the lengthening of the Ni-Ni distances in 2.…”