[Cp*W(dmit)2]•: An Organometallic 15-Electron Neutral Radical (d1) with Optical Limiting Properties in Solution and an Antiferromagnetic Ground State in the Solid State

Abstract

The synthesis of the organometallic d2 [Cp*W(dmit)2]1– complex (where Cp* is pentamethylcyclopentadienyl and dmit is 1,3‐dithiole‐2‐thione‐4,5‐dithiolate), and its oxidation to the paramagnetic d1 [Cp*W(dmit)2]• species, is described and their X‐ray crystal structures given. Geometrical evolutions upon oxidation, characterized by a variable folding of the WS2C2 metallacycles along the S–S hinge, are rationalized by density functional theory (DFT) calculations and by comparison with the molybdenum analogs; as is also the evolution in the UV‐vis‐NIR absorption spectra. In solution, only the d1 complexes exhibit positive optical density variations in transitory nanosecond spectroscopy after 10 ns laser pulses. A weak optical limiting effect was observed on these d1 species, stronger in the W than in the Mo complex. In the solid state, the interacting, paramagnetic [Cp*W(dmit)2]• species (θCurie–Weiss = –20 K) orders antiferromagnetically below TNéel = 4.5 K with a spin‐flop field, BSF(W) of 8000 G. Compared with the molybdenum analog, the weaker θCurie–Weiss(W) and TNéel(W) values, and larger BSF(W) values reflect weaker intermolecular interactions due to a decreased spin density on the dithiolene ligands and stronger spin–orbit coupling with the W atom, as confirmed by DFT calculations on the d2 and d1 Mo and W complexes.

Formations and electrochemical behavior of mononuclear and binuclear molybdenum dithiolene complexes with nitrosyl ligands: Evidence for the formation of a coordinatively unsaturated species [Cp∗Mo(NO)(dithiolene)]

“…Fourmigué et al already reported the Cp * M bisdithiolene complexes [Cp * M(dmit) 2 ] n (M = Mo [10] and W [28]; n = À1 and 0). According to their articles, when the complex is the monoanion [Cp * M(dmit) 2 ] À (M = d 2 metal), two metalladithiolene rings are planar, however, in the neutral complex [Cp * M(dmit) 2 ] 0 (M = d 1 metal), one of the two metalladithiolene rings is distorted.…”

Nonlinear Optical Materials for the Smart Filtering of Optical Radiation

“…The reacted copper , ( 37 , Chart ) and tungsten or molybdenum ( 38a , b , Chart ) dithiolene complexes have also been tested for third-order optical nonlinearities. Complex 37 was tested by Z -scan technique with ps and ns laser pulses in the NIR region.…”

“…TPA has been found when the sample solution was irradiated by 40 ps pulse width at 1064 nm and the TPA coefficient was 4 × 10 –13 m/W. , Upon excitation with 15 ns laser pulses at 1053 nm, the Z -scan profiles revealed strong RSA. The nonlinear absorption coefficient was found to be 7.07 × 10 –11 m/W. , On the other hand, complex 38a , along with complex 38b (Chart ), exhibited weak OL effect …”

“…On the other hand, when irradiated with a 15 ns laser pulse, a stronger RSA was found, with nonlinear optical absorption coefficients in the order of 10 −10 m/W. The reacted copper 655,656 (37, Chart 10) and tungsten or molybdenum 657 (38a,b, Chart 10) dithiolene complexes have also been tested for third-order optical nonlinearities. Complex 37 was tested by Z-scan technique with ps and ns laser pulses in the NIR region.…”

“…655,656 On the other hand, complex 38a, along with complex 38b (Chart 10), exhibited weak OL effect. 657 Other metal complexes, (Me Figure 33 shows the transmitted fluence as a function of the incident fluence. At lower energy, the optical response obeys Beer's law.…”