Instituto de Tecnologia Química e Biológica, UNL, Av. da República - EAN, 2780-157, Oeiras, Portugal.
Dalton Trans. 2010 Oct 28;39(40):9579-87. doi: 10.1039/c0dt00340a. Epub 2010 Sep 3.
The hexaazamacrocycles 28(2)N(6) {cyclo[bis(4,6-dimethyldibenzo[b,d]furaniminoethyleneiminoethylene]} and 32(2)N(6) {cyclo[bis(4,6-dimethyldibenzo[b,d]furaniminopropyleneiminopropylene]} form stable dinuclear copper(ii) complexes suitable to behave as receptors for several anionic substrates. These two receptors were used to study the binding interactions with several substrates, such as imidazole (Him) and some carboxylates [benzoate (bz(-)), oxalate (ox(2-)), malonate (mal(2-)), phthalate (ph(2-)), isophthalate (iph(2-)), and terephthalate (tph(2-))] by spectrophotometric titrations and EPR spectroscopy in MeOH (or H(2)O):DMSO (1 : 1 v/v) solution. The largest association constant was found for ox(2-) with Cu(2)32(2)N(6)(4+), whereas for the aromatic dicarboxylate anions the binding constants follow the trend ph(2-) > iph(2-) > tph(2-), i.e. decrease with the increase of the distance of the two binding sites of the substrate. On the other hand, the large blue shift of 68 nm observed by addition of Him to Cu(2)32(2)N(6)(4+) points out for the formation of the bridged CuimCu cascade complex, indicating this receptor as a potential sensor for the detection and determination of imidazole in solution. The X-band EPR spectra of the Cu(2)28(2)N(6)(4+) and Cu(2)32(2)N(6)](4+) complexes and the cascade complexes with the substrates, performed in H(2)O:DMSO (1 : 1 v/v) at 5 to 15 K, showed that the CuCu distance is slightly larger than the one found in crystal state and that this distance increases when the substrate is accommodated between the two copper centres. The crystal structure of [Cu(2)28(2)N(6)(ph)(2)]·CH(3)OH was determined by X-ray diffraction and revealed the two copper centres bridged by two ph(2-) anions at a CuCu distance of 5.419(1) Å. Each copper centre is surrounded by three carboxylate oxygen atoms from two phthalate anions and three contiguous nitrogen atoms of the macrocycle in a pseudo octahedral coordination environment.
六元大环28(2)N(6){环[双(4,6-二甲氧基二苯并[b,d]呋喃亚基乙烯亚基乙烯)}和32(2)N(6){环[双(4,6-二甲氧基二苯并[b,d]呋喃亚基丙烯亚基丙烯]}形成稳定的双核铜(ii)配合物，适合作为几种阴离子底物的受体。这两种受体被用于通过分光光度滴定和 EPR 光谱法研究与几种底物的结合相互作用，例如咪唑（Him）和一些羧酸盐[苯甲酸酯（bz(-)），草酸盐（ox(2-)），丙二酸盐（mal(2-)），邻苯二甲酸酯（ph(2-)），间苯二甲酸酯（iph(2-)）和对苯二甲酸酯（tph(2-)）]在 MeOH（或 H(2)O）：DMSO（1：1v/v）溶液中。发现 ox(2-)与 Cu(2)32(2)N(6)(4+)的结合常数最大，而对于芳族二羧酸根阴离子，结合常数遵循 ph(2-)>iph(2-)>tph(2-)的趋势，即随着底物两个结合位点之间距离的增加而降低。另一方面，向 Cu(2)32(2)N(6)(4+)中添加 Him 观察到的 68nm 大蓝移表明形成桥接的 CuimCu级联配合物，表明该受体作为检测和测定溶液中咪唑的潜在传感器。在 5 至 15 K 下在 H(2)O：DMSO（1：1v/v）中进行的 Cu(2)28(2)N(6)(4+)和 Cu(2)32(2)N(6)](4+)配合物和级联配合物的 X 波段 EPR 光谱表明，CuCu 距离略大于晶体状态下发现的距离，并且当底物容纳在两个铜中心之间时，该距离会增加。[Cu(2)28(2)N(6)(ph)(2)]·CH(3)OH 的晶体结构通过 X 射线衍射确定，并显示出由两个 ph(2-)阴离子桥接的两个铜中心，CuCu 距离为 5.419(1)Å。每个铜中心被来自两个邻苯二甲酸根阴离子的三个羧酸盐氧原子和大环中的三个相邻氮原子包围，形成近似八面体配位环境。
