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Новости химической науки > Необычная структура и свойства бората калифорния5.6.2015 
 Самый тяжелый из химических элементов, который можно в разумных количествах обнаружить в Земной коре, калифорний, способен образовывать необычную ковалентную связь с борат-анионом, что в соответствии с результатами теоретических и экспериментальных исследований существенно изменяет электронные свойства иона калифорния.
Полученные результаты оспаривают прежде бытовавшие воззрения о том, что калифорний, плутоний и америций способны образовывать химические связи с исключительно ионным характером.
Эта информация позволит найти новые способы оптимизации взаимодействия таких химических элементов, как америций, берклий и калифорний в составе их соединений, что может оказаться полезным для оптимизации их разделения и вторичной переработки отработанного ядерного топлива.
Полиборат-анион «обертывает» катионы калифорния таким образом, что калифорний проявляет координационное число 8 (слева). Зеленое свечение, которым отличается борат калифорния, демонстрирует черты, более характерные для производных металла с большим зарядом. (Рисунок из Nature Chemistry 6, 387 (2014) DOI: 10.1038/nchem.1896)
Десятилетиями идут споры о том, как внешние валентные оболочки актиноидов участвуют в образовании химических связей. Недавние экспериментальные и квантово-химические исследования демонстрируют, что для ранних актиноидов, к которым, например, относится уран, вклад в связывание вносят внешние орбитали –7p, 7s, 6d и/или 5f. Тем не менее, результаты прямых структурных исследований и спектральные характеристики демонстрируют, что с увеличением заряда ядра актиноида понижается доля ковалентного связывания и увеличивается степень ионности химической связи.
Предполагается, что такие поздние актиноиды, к которым относится и калифорний, отличаются способностью к образованию химических связей с большой степенью ионности – подобный тип взаимодействия характерен для производных лантаноидов. Для того чтобы подтвердить или опровергнуть химическое сходство лантана и калифорния исследователи «обернули» ион калифорния в исключительно электроноизбыточное окружение, используя лиганд-полиборат, который отличается высокой поляризуемостью, а также может существенно перегруппировываться после комплексообразования.
Электроны лиганда донировались на валентные орбитали калифорния, и, к своему удивлению, исследователи обнаружили, что в связывание вовлечены орбитали 5f, 6d, 7s и 7p калифорния, и для образующегося соединения наблюдается значительное влияние поля лигандов. Результаты синтезов, структурного и спектрального исследования бората калифорния согласуются с данными квантово-химических расчетов. Полученные результаты позволяют говорить о том, что химия калифорния необычна и может рассматриваться как промежуточное звено между химией d-элементов, как, например, меди и платины, и химией лантаноидов и актиноидов.
Источник: Nature Chemistry 6, 387 (2014) DOI: 10.1038/nchem.1896 метки статьи: #неорганическая химия, #природа химической связи Перепечатка статьи разрешается при условии размещения активной гиперссылки на ChemPort.Ru Комментарии к статье:
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med of.
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Marriage ceremony magazines are actually great towards compare colors and patterns.When you're ready to order a gown do have a go on to start with as you ought to get the right size.Many times yourself in your awkward position to be in concerning sizes and when the case ensure you order the sole that's larger as you can have the item altered to put.Make absolutely sure to gather the landing date of your gown.Try to have your ensemble delivered one 6 weeks before hand to give you lot's with room for just about any altering and then choose accessories which may add to barefoot jogging.
If acquiring your gown by a bridal sepcialist be forewarned that some of them by default is going to order ones gown one size too big.This are able to produce even more charges as time goes on as you ought to have the gown fitted so ensure you ask up front for the values for further altering.Understand that gowns are generally late within arriving so in place of adding extra stress to your already rather busy life just order well before you go.
Make sure you remember The Special message And Toasts One ingredient of weddings is actually delivering the perfect best mankind wedding speech which is a complex responsibility for most people men.There are facts to consider, like whether or not the speech could be humorous and / or safe as well as serious.In addition there are websites nowadays that serve free preferred man speeches.Just be sure to give this in the best mankind well earlier than schedule so he has time to help you customize the idea (:--).You can also find classic short wedding day toast examples to boot.
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