Complexes with Alkynyl and Vinylidene Ligands

880 X 10 ° esu V( S o) = 350 x 10 ° esu measured by HRS) structures have been synthesized and investigated [150]. They involve very large static and dynamic hyperpolarizabilities with an improved efficiency/transparency trade-off for SHG applications (e.g., 37, /Lav = 477 nm vs 41, = 459 nm). 

ApplicatiOTis of these molecular NLO chromophores, to produce second-order bulk NLO materials or structured Aims, are very limited. Actually, in spite of their veiy large molecular hyperpolarizabilities, they exhibit crystalline materials with modest bulk SHG efficiency [11], e.g., the most efficient crystalline material shows a powder efficiency of only eight times that of urea [11], in consequence of the reluctance of acetylide complexes to crystallize in noncentrosymmetric structures. 

In the last few years, this class of molecular materials has attracted renewed interest by virtue of their remarkable third-order NLO properties [11, 19, 150]. 

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