Near-infrared absorbing dyes at 1064 nm: Soluble dithiolene nickel complexes with alkylated electron-donating groups as Peripheral substituents

•Soluble dithiolene nickel complexes are synthesized as NIR absorbing dyes.•Dithiolene ligands in carbazole-containing nickel complex take radical monoanion.•Substituent electron-donating ability changes chemical state of molecular core.•The resulting complexes take on a glassy state at low temperature.•Dithiolene nickel complexes could be applied to NIR laser protection at 1064 nm.

Soluble dithiolene nickel complexes are designed and synthesized as near-infrared (NIR) absorbing dyes through the introduction of strong electron-donating groups at the molecular periphery. The resulting complexes are characterized by 1H/13C NMR, IR, ESI-MS, UV–vis–NIR, TG, DSC, XPS and elemental analysis. The identification results are in accord with the chemical structure of designed dithiolene nickel complexes. The XPS results suggested that the dithiolene ligands in carbazole-containing nickel complex take a radical monoanion, which depends on the substituent electron-donating ability to a large extent. The TG and DSC measurements indicated that the resulting complexes have an excellent thermal stability and take on a glassy state at low temperature. The laser transmittance measurement suggested that the optical filters fabricated through static solution-casting approach with dithiolene nickel complexes as NIR absorbing dyes could be well applied to the NIR laser protection at 1064 nm.

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