One of Vincent van Gogh’s last paintings before his suicide, an 1890 portrait of his innkeeper’s teen-age daughter, sold at auction in New York for a disappointing $12.5 million. “Portrait of Adeline Ravoux,” sold at Christie’s auction house, was expected by art experts to bring $15 million. The buyer, who bid by telephone, was not immediately identified. Over the last 14 months, three of Van Gogh’s paintings have fetched previously unheard-of multimillion-dollar prices that shook the art world. One, titled “Irises,” made history in November when it sold at Sotheby’s in New York for $53.9 million, the highest price paid at auction for a painting.