Information on the Chaki or De Leon Families in Instanbul in the 19th Century

Hello, my name is Iris and I am doing some genealogy on the Chaki and De Leon families who were Sephardic Jews and lived in Istanbul in the late 1800s/early 1900s. I am having a lot of trouble finding much on them and I would appreciate recommendations on where I could get more information. This is what I know about them. I am sure of Rebecca Chaki, born in Istanbul in 1875 and died at a death camp in Poland in 1943. She was deported from France. She had three daughters and a son that I am aware of and all the children were born in Turkey but none stayed there. One daughter, Elis Chaki, married the British explorer and historian, COL Stewart Francis Newcombe. I have a lot of information on her descendants. A son Joseph Chaki was believed to have moved to England before WWII and two other sisters were in France or England when the war started. I am not sure but I believe Rebecca's husband was Isaac or Elijah Chaki who was born in Turkey as well between 1850-1875. Her father was a De Leon and supposedly a famous banker or jeweler of the Sultan under the Ottomans. Thank you so much for your help in advance.