McConnell entered University College Dublin (UCD) in 1932 and graduated in 1936 with a first-class honours master's degree in mathematics.
He was made a Doctor of Mathematical Sciences by the Royal University of Rome (La Sapienza) in 1941.
[2] He is best known for research on Rotational Brownian motion, the electric and magnetic properties of matter and the theory of the negative proton (or anti-proton).
[1] McConnell was the 1986 recipient of the RDS Irish Times Boyle Medal for Scientific Excellence.
[3] He was appointed to the Pontifical Academy of Sciences in 1990, and honoured with the title of Monsignor by Pope John Paul II in 1991.