Optical power limiters based on colorless di-, oligo-, and polymetallaynes: Highly transparent materials for eye protection devices

The synthesis, characterization, and photophysics of a series of solution-processable and tractable di-, oligo-, and polymetallaynes of some group 10-12 transition metals are presented. Most of these materials are colorless with very good optical transparencies in the visible spectral region and exhibit excellent optical power limiting (OPL) for nanosecond laser pulse. Their OPL responses outweigh those of the state-of-the-art reverse saturable absorption dyes such as C₆₀, metalloporphyrins, and metallophthalocyanines that are all associated with very poor optical transparencies. On the basis of the results from photophysical studies and theoretical calculations, both the absorption of triplet and intramolecular charge-transfer states can contribute to the enhancement of the OPL properties for these materials. Electronic influence of the type, spatial arrangement, and geometry of metal groups on the optical transparency/nonlinearity optimization is evaluated and discussed in detail. The positive contribution of transition metal ions to the OPL of these compounds generally follows the order: Pt > Au > Hg > Pd. The optical-limiting thresholds for these polymetallaynes can be as low as 0.07 J cm^-2 at 92 % linear transmittance and these highly transparent materials manifest very impressive figure of merit σ_ex/σ_o values (up to 22.48), which are remarkably higher than those of the benchmark C₆₀ and metal phthalocyanine complexes. The present work demonstrates an attractive approach to developing materials offering superior OPL/optical transparency trade-offs and these metallopolyynes are thus very promising candidates for use in practical OPL devices for the protection of human eyes and other delicate optical sensors.