The new capital means that Barclays will not have to receive funding from the British government, unlike some of its competitors, amid the international financial crisis.
The announcement ensures that Barclays meets higher capital targets which were set by Britains Financial Services Authority earlier this month.
"The Board of Directors of Barclays today announces a proposal to raise up to 7.3 billion pounds of additional capital from existing and new strategic and institutional investors," the bank said in a statement.
Sovereign wealth fund Qatar Holding will invest two billion pounds, and has subscribed for warrants to purchase a further 1.5 billion pounds of ordinary Barclays shares.
Abu Dhabis Sheikh Mansour Bin Zayed Al Nahyan, meanwhile, will provide 3.5 billion pounds, and has also subscribed for 1.5 billion pounds in ordinary share warrants.
Challenger, which is owned by Sheikh Hamad Bin Jassim Bin Jabr Al-Thani, the chairman of Qatar Holding, will invest a further 300 million pounds into Barclays.
The remaining 1.5 billion pounds will be issued to other institutional investors.