Joseph Neubauer, the Barnes board's vice chairman, praised Gillman for his management of the Barnes move, which was the subject of lengthy and contentious litigation, and for strengthening operations and building programming at the Parkway location.
"Derek has successfully led the Barnes through a remarkable period of transition and transformation, enabling the foundation to better advance Albert Barnes' great vision," Neubauer said in a statement.
The new Barnes gallery facility, housing a virtually unmatched collection of impressionist and early modern art assembled by patent-medicine king Albert C. Barnes, represents Gillman's second major cultural project in Philadelphia.
Previously, as head of the Pennsylvania Academy of the Fine Arts for seven years, he spearheaded the capital campaign for and renovation of what is now the academy's Hamilton Building at Broad and Cherry Streets. The building provides exhibition space for the academy's museum, and studio and classroom space for its school.
Gillman, born in Brighton, England, and a former deputy director of the National Gallery of Victoria in Melbourne, Australia, said he was eager to return to teaching.
"Working with a terrific team of trustees and colleagues, I have achieved all I had hoped to for the Barnes - and more," he said in a statement. He praised the work of Tod Williams and Billie Tsien, the architects of the new gallery, and said he took satisfaction in what he deemed a successful effort "to stabilize the finances, to build the staff, expand programming" at the Barnes in Philadelphia.
After arriving at the Barnes in 2006, Gillman oversaw the completion of a successful $200 million capital and endowment campaign, construction of the $150 million gallery, the expansion of staff and programming, and attendance that jumped from 60,000 annually to 325,000.
But the move was not smooth sailing in the courts. When Gillman arrived, Montgomery County Orphans' Court, which has jurisdiction over trusts, had already ruled that the Barnes could move to Philadelphia, despite the strictures of its founder that it remain in Merion in perpetuity. The court deemed a move the least disruptive way for the institution to avoid potentially catastrophic bankruptcy proceedings.
After Gillman arrived, opponents of the move filed two more legal actions to force the foundation to stay. Both failed.
"Those were not the most bump-free times on the road," Gillman said in an interview Tuesday. "I wouldn't expect, nor do I think the board expected, two more lawsuits filed over those years . . . . Conversely, because people saw this as something we could not pull off, it was immensely satisfying that we did pull it off."
The new facility opened in May 2012 and has been operating at or near capacity ever since.
"The Barnes is really well-positioned for the future and I am excited about going back into higher education, where I have spent half of my career and where I can apply my experience in institution-building along with my long-standing academic interests," Gillman said.
Barnes trustees have formed a search committee and have hired an outside consultant to help in the effort to find Gillman's successor. Margaret Zminda, the foundation's executive vice president, and chief financial and operating officer, will serve as interim chief executive.
"The challenges are not as insurmountable as they were in 2007," Zminda said. "I think the work Derek and I accomplished, together with our team, is pretty great. Now that we've pulled this part of it off, the question is - what next? The answer to that isn't fully formed yet."