An organic light-emitting device comprising: an anode; a cathode; a light-emitting layer located between the anode and the cathode, said light-emitting layer containing a light-emitting metal complex comprising general formula 1: (1) where M represents Re(I), W(0), Ir(III), or Os(II); L1 represents a tridentate ligand; and L2, L3 and L4 represent ligands, characterised in that L1 comprises general formula 2:(2) where R1 represents a bridging group; and Ar1, Ar2 and Ar3 each independently represents a group comprising a heteroaryl ring and * indicates coordination to M.