2,2′-Bipyridines carrying a diazo moiety and their complexes with bis(hexafluoroacetylacetonato)copper: synthesis, structures, electronic and magnetic properties of their photoproducts in frozen solutions
作者:Hiroshi Morikawa、Fumika Imamura、Yasuo Tsurukami、Tetsuji Itoh、Harumi Kumada、Satoru Karasawa、Noboru Koga、Hiizu Iwamura
DOI:10.1039/b007375j
日期:——
4-(α-Diazobenzyl)-2,2'-bipyridine 2, diazodi4-(2,2'-bipyridyl)}methane 3, and 1,3-benzenediyl4-(4'-methyl-2,2'-bipyridyl)diazomethane} 4 were prepared as new types of spin sources/magnetic
couplers. The molecular structures of bipyridine ligands, 2, 3, 4,
and [Cu(hfac)2·2]
were revealed by X-ray analyses. Photolysis of 2, 3, 4,
and their complexes with Cu(hfac)2 in MTHF frozen solutions
at cryogenic temperature was followed by UV–Vis and EPR spectroscopy.
UV–Vis and EPR spectra after photolysis showed strong two absorptions;
at 508 and 471 nm for 2,
and 511 and 476 nm for 3,
and characteristic sets of EPR signals due to the triplet states; |D/hc| = 0.418,
and 0.436 cm−1 and |E/hc| = 0.021
and 0.022 cm−1 for 2
and 3, respectively. Diazo compound 4 after photolysis also showed absorptions at
506 and 471 nm and EPR signals characteristic of a quintet. Their complexes
with Cu(hfac)2 showed a red shift of 3–14 nm
in the visible spectra and gave EPR spectra characteristic of the high-spin
complexes under similar conditions. Magnetic susceptibility measurements on
a SQUID magnetometer were carried out using a sample similar to the one employed
in the UV–Vis and EPR studies. The field dependence of magnetization
in frozen solution suggested that the ground-state spin multiplicities
of the photoproducts of 2, 3, and 4
were triplet, triplet, and quintet, respectively. Similarly, those of their
complexes with Cu(hfac)2 were quartet, quintet, and septet,
respectively.
制备了三种新型自旋源/磁耦合剂:4-(α-重氮苄基)-2,2'-联吡啶2、二氮二4-(2,2'-联吡啶)}甲烷3和1,3-苯二亚甲基4-(4'-甲基-2,2'-联吡啶)二氮甲烷}4。通过X射线分析揭示了联吡啶配体2、3、4和[Cu(hfac)2·2]的分子结构。在低温下,对2、3、4及其与Cu(hfac)2的配合物在MTHF冷冻溶液中的光解过程进行了UV-Vis和EPR光谱跟踪。光解后的UV-Vis和EPR光谱显示出强烈的两个吸收峰:2在508和471 nm,3在511和476 nm,以及由于三重态状态产生的特征EPR信号:|D/hc| = 0.418和0.436 cm−1,|E/hc| = 0.021和0.022 cm−1分别为2和3。光解后,二氮化合物4也显示出在506和471 nm处的吸收峰和特征的五重态EPR信号。它们的Cu(hfac)2配合物在可见光谱中表现出3-14 nm的红移,并在相似条件下给出高自旋配合物的特征EPR光谱。使用在UV-Vis和EPR研究中采用的类似样品,在SQUID磁强计上进行了磁化率测量。在冷冻溶液中的磁化场依赖性表明,2、3和4的光解产物基态自旋多重性分别为三重态、三重态和五重态。同样,它们与Cu(hfac)2的配合物的基态自旋多重性分别为四重态、五重态和七重态。