A joint venture of Philadelphia-based Rubenstein Partners and Nordblom Cos. of Burlington has acquired the 1000 Washington office building in Boston’s South End for $75 million.

The developers anticipate office rents will rise in the rapidly-changing neighborhood. The 242,000-square-foot building is across the street from the Ink Block mixed-use development at the former Boston Herald property that includes luxury apartments and condos under construction and a Whole Foods Market that opened earlier this month.

“It’s difficult to peg the rents because it’s 100 percent leased, but we feel the rents have gone up and will continue to go up as the area improves,” said Deke Schultze, New England director for Rubenstein Partners.

In 2012, the city enacted a new zoning district for the Harrison Avenue and Albany Street corridor designed to encourage more mixed-use developments and revitalize the neighborhood with new housing and commercial projects.

Troy Boston, a 378-unit residential development, also is under construction at 275 Albany St. in a venture by Gerding Edlen and Normandy Real Estate Partners.

The recent purchase was financed with a $51 million mortgage from East Boston Savings Bank, arranged by HFF. The seller was Teraview Investments LLC, a realty trust affiliated with Nordblom Co. Teraview acquired the property in 2006 for $34.75 million, according to Suffolk County Registry of Deeds records.

The 11-story building contains a 310-car garage, top-floor cafeteria and fitness center with locker rooms. Tenants include food services company Unidine Corp. and National Indemnity Co.

Rubenstein’s existing investments in Greater Boston include 55 Walkers Brook Drive in Reading, the CenterPoint office park in Waltham and 495 Business Center in Tewksbury.

“We’re excited about this because it’s our first downtown investment,” Schultze said.