Cyclic Polyether와 금속염과의 착물형성에 관한 연구

Abstract

Cyclic Polyether(18개 원자 고리형 폴리에테르)와 알칼리금속염(NaSCN, KSCN) 착물의 안정도상수를 ~10?M의 일정한 이온강도로 유지한 아세토니트릴 용매에서 전도도법에 의해 측정하였다. K?이온에 대한 안정도상수는 18C6>DCC>B18C6>DMDBC>AmDBC∼DBC>NDBC의 순이고, Na?고온은 DCC>DMDBC>AmDBC∼DBC>B18C6>18C6>NDBC의 순으로 감소하였다. 예측과 다른 순위변화는 고리내 산소원자들의 염기도 또는 치환기들에 의한 입체효과 등에 의한 설명은 충분치 못하며, 이들 Crown화합물들의 구조변화효과를 고려해야 한다. 또한 DBC계열에 대한 양이온들의 안정도는 Na?이온이 K?이온보다 커서 이온-공동 반경개념에 어긋나는데, 이것 역시 구조변화효과를 중요한 인자로 고려해야 한다.

The stability constants for the complexes of cyclic polyethers (18-membered macrocycles) with alkali metal salts(NaSCN, KSCN) in Acetonitrile have been determined conducto-metrically at constant ionic strength of ∼10­³M. For the potassium cation the stability constants are decrease in the order:18C6>DCC>B18C6>DMDBC>AmDBC∼DBC>NDBC, whereas for the sodium cation : DCC>DMDBC>AmDBC∼DBC>B18C6>18C6>NDBC. Such anomalous order of stability constants must be attributed to conformational changes in the macrocyclic ring rather than the basicity of oxygens or steric effects of substituents. The interations of the alkali metal cations with series of DBC are substantially more favorable for the sodium ion than for the potassium ion in Acetonitrile. This result is the reverse of that predicted from the ion-cavity radius concept. From these results, the conformational changes are very important factors for the stabilities of the complexes in Acetonitrile.

The stability constants for the complexes of cyclic polyethers (18-membered macrocycles) with alkali metal salts(NaSCN, KSCN) in Acetonitrile have been determined conducto-metrically at constant ionic strength of ∼10­³M. For the potassium cation the stability constants are decrease in the order:18C6>DCC>B18C6>DMDBC>AmDBC∼DBC>NDBC, whereas for the sodium cation : DCC>DMDBC>AmDBC∼DBC>B18C6>18C6>NDBC. Such anomalous order of stability constants must be attributed to conformational changes in the macrocyclic ring rather than the basicity of oxygens or steric effects of substituents. The interations of the alkali metal cations with series of DBC are substantially more favorable for the sodium ion than for the potassium ion in Acetonitrile. This result is the reverse of that predicted from the ion-cavity radius concept. From these results, the conformational changes are very important factors for the stabilities of the complexes in Acetonitrile.