NEW YORK (TheStreet) -- TheStreet (TST) said it agreed to pay $21 million in cash for Management Diagnostics, the London-based developer of a relationship capital management service used by law firms, investment banks and consultancies. The transaction is scheduled to be closed during the fourth quarter, the company said.

Management Diagnostics' main product is BoardEx, a proprietary people database used by institutions to "leverage their relationships and facilitate business and corporate development initiatives," TheStreet said. Founded in 1999, Management Diagnostics has offices in London, New York and Chennai, India. The service will be integrated into The Deal, TheStreet's business unit that provides Wall Street dealmakers with proprietary analysis of mergers, acquisitions and other transactions.

"The acquisition of BoardEx advances the strategic objectives of TheStreet by increasing both institutional content and subscribers," said Elisabeth DeMarse, president, chairman and CEO of TheStreet. BoardEx's customers will provide the company a predictable source of recurring revenue, she said.

"Combining with The Deal elevates BoardEx," said James Daly, CEO of BoardEx. "Knowing a company might be in play is one thing, but knowing who to call and how to influence them is a game-changer."

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This article was written by a staff member of TheStreet.