Oxygen Gas Sensing by Luminescence Quenching in Crystals of Cu(xantphos)(phen)⁺ Complexes

We have shown that crystals of the highly emissive copper(I) compounds [Cu(POP)(dmp)]tfpb, [Cu(xantphos)(dmp)]tfpb, [Cu(xantphos)(dipp)]tfpb, and [Cu(xantphos)(dipp)]pftpb, (where POP = bis[2-(diphenylphosphino)phenyl]ether; xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; dmp = 2,9-dimethyl-1,10-phenanthroline; dipp = 2,9-diisopropyl-1,10-phenanthroline (dipp); tfpb− = tetrakis(bis-3,5-trifluoromethylphenylborate); and pftpb = tetrakis(pentfluorophenyl)borate) are oxygen gas sensors. The sensing ability correlates with the amount of void space calculated from the crystal structures. The compounds exhibit linear Stern−Volmer plots with reproducible KSV constants from sample to sample; these results reinforce the observations that the sensing materials are crystalline and the sensing sites are homogeneous within the crystals. The long lifetime (∼30 μs), high emission quantum yield (ϕ = 0.66), appreciable KSV value (5.65), and very rapid response time (51 ms for the 95% return constant) for [Cu(xantphos)(dmp)]tfpb are significantly better than those for the [Cu(NN)2]tfpb complexes studied previously and compare favorably with [Ru(4,7-Me2phen)3](tfpb)2, (KSV = 4.76; 4,7-Me2phen = 4,7-dimethyl-1,10- phenanthroline). The replacement of precious metals (like Ru or Pt) with copper may be technologically significant and the new compounds can be synthesized in one or two steps from commercially available starting materials. The strictly linear Stern−Volmer behavior observed for these systems and the absence of a polymer matrix that might cause variability in sensor to sensor sensitivity may allow a simple single-reference point calibration procedure, an important consideration for an inexpensive onetime limited use sensor that could be mass produced.我们已证实，高发光铜(I)配合物[Cu(POP)(dmp)]tfpb、[Cu(xantphos)(dmp)]tfpb、[Cu(xantphos)(dipp)]tfpb以及[Cu(xantphos)(dipp)]pftpb的晶体（其中POP = 双[2-(二苯基膦基)苯基]醚（bis[2-(diphenylphosphino)phenyl]ether）；xantphos = 4,5-双(二苯基膦基)-9,9-二甲基氧杂蒽（4,5-bis(diphenylphosphino)-9,9-dimethylxanthene）；dmp = 2,9-二甲基-1,10-菲咯啉（2,9-dimethyl-1,10-phenanthroline）；dipp = 2,9-二异丙基-1,10-菲咯啉（2,9-diisopropyl-1,10-phenanthroline）；tfpb⁻ = 四(3,5-双(三氟甲基)苯基)硼酸根（tetrakis(3,5-bis(trifluoromethyl)phenyl)borate）；pftpb = 四(五氟苯基)硼酸根（tetrakis(pentafluorophenyl)borate））可作为氧气气体传感器。其传感性能与通过晶体结构计算得到的空隙体积密切相关。该类配合物呈现线性斯特恩-沃尔默（Stern-Volmer）曲线，且不同样品间的斯特恩-沃尔默常数（KSV）重现性良好；这一结果佐证了传感材料为晶体、且晶体内部传感位点均一的结论。以[Cu(xantphos)(dmp)]tfpb为例，其长发光寿命（约30 μs）、高发光量子产率（ϕ = 0.66）、可观的KSV值（5.65）以及极快的响应时间（达到95%响应恢复的时间为51 ms），均显著优于此前研究的[Cu(NN)₂]tfpb配合物，且与[Ru(4,7-Me₂phen)₃](tfpb)₂（KSV = 4.76；4,7-Me₂phen = 4,7-二甲基-1,10-菲咯啉）性能相当。用铜替代贵金属（如钌(Ru)或铂(Pt)）具有重要的技术价值，且该类新型配合物可通过一步或两步反应由商业化起始原料合成。此类体系展现出严格的线性斯特恩-沃尔默行为，且无需使用可能导致传感器间灵敏度差异的聚合物基质，因此可采用简单的单参考点校准流程——这对于可大规模生产的低成本一次性有限使用传感器而言是一项关键优势。