Third-order nonlinear optical properties of silver phenylacetylides

Research of the third-order nonlinear optical (NLO) materials based on transition metal coordination complexes applicable to ultrafast response devices has attracted much interests in recent years. Silver phenylacetylide (AgC≡CPh) for scores of years has been regarded as a coordination polymer. Its prominent potential as NLO material has been realized here for the first time, and found to be comparable to those of representative conjugated organic polymers.; Definite molecular weight for a sample is necessary for NLO susceptibility calculations, but such data are very difficult to obtain for AgC≡CPh and most of the silver thiolates due to solubility problems. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry has been successfully applied to characterize AgC≡CPh and silver thiolates, [AgSR(Ar)]. In each case the monomer units remained intact during ionization, and the molecular ions were produced through silver cationization, with a general molecular ion formula [nM+Ag]+. Molecular ion peaks of AgC≡CPh up to [AgC≡CPh]20 were apparently observed. The most abundant peaks for AgC≡CPh and AgSR(Ar) were always [4M+Ag]+.; The third-order NLO susceptibility, χ(3), was measured by the heterodyned optical Kerr effect method. The χ(3) and the second-order hyperpolarizability γ for AgC≡CPh were 2.4 × 10−14esu and 5.18 × 10−32 esu, respectively, much higher than those of the heptameric polyphenylacetylene under the same conditions. A strategy for the enhancement of the optical nonlinearity via the formation of double salts of AgC≡CPh with silver thiolates was engineered. The γ values of the [AgC≡CPh-AgStBu] and [AgC≡CPh-AgSC₆H₂Me₃] were enhanced by one order of magnitude, and that of the [AgC≡CPh-AgSC₆H ₂iPr₃] was noticeably enhanced by two orders of magnitude as compared with that of [AgC≡CPh], due to the enhanced charge transfer and the formation of extended conjugated system.; Quantum chemical calculation based on density functional theory confirms that AgC≡CPh is a coordinated polymeric compound. Molecular modeling suggests that the interconnecting linkage between AgC≡CPh molecules is through η6-benzene to Ag atom mode, rather than through η 2-acetylene to Ag atom mode. Molecular modeling also suggests that the interaction between [AgC≡CPh]₄ and [AgSC₆H ₂iPr₃]₄ is through S → Ag bonding.; Study of optical limiting (OL) effect showed that the OL effect of conjugated organic polymers could be improved by doping with AgNO₃. Modification of C₆₀ with transition organometallic complex is an effective way to enhance its OL performance. Paramagnetic transitional metallic complex seems significantly active.