Table 1. Optimization studies ^a .

Entry	Catalyst	Solvent	Yield b (%)
1	Co(dmgH)pyCl	CH3CN	17 (20 : 1)
2	Co(dmgH)pyCl	THF	14 (7 : 1)
3	Co(dmgH)pyCl	DCE	44 (7 : 1)
4	Co(dmgH)2(4-NMe2py)Cl	DCE	70 (12 : 1)
5	Co(dmgH)(dmgH2)Cl2	DCE	14 (2 : 1)
6	None	DCE	n.d.
7 c	Co(dmgH)2(4-NMe2py)Cl	DCE	n.d.
8 d	Co(dmgH)2(4-NMe2py)Cl	DCE	n.d.

^aConditions: 1a (0.20 mmol), 2a (0.4 mmol), Acr⁺-Mes ClO₄^– (3 mol%) and co-catalyst (10 mol%) were added in solvent (2 mL) under N₂ and irradiated by blue LEDs for 24 h.

^bYields were determined by GC with naphthalene as the internal standard and are the sum of the cis and trans isomers. The ratio of the E/Z isomers are shown in parenthesis.

^cReaction was performed without photosensitizer.

^dReaction was carried out in the dark.