The INTEGRAL and Swift hard X-ray surveys have identified a large number of new sources , among which many are proposed as Cataclysmic Variables ( CVs ) .
Here we present the first detailed study of three X-ray selected CVs , Swift J1907.3-2050 , IGR J12123-5802 , and IGR J19552+0044 based on XMM-Newton , Suzaku , Swift observations and ground based optical and archival nIR/IR data .
Swift J1907.3-2050 is highly variable from hours to months-years at all wavelengths .
No coherent X-ray pulses are detected but rather transient features .
The X-ray spectrum reveals a multi-temperature optically thin plasma absorbed by complex neutral material and a soft black body component arising from a small area .
These characteristics are remarkably similar to those observed in magnetic CVs .
A supra-solar abundance of nitrogen could arise from nuclear processed material from the donor star .
Swift J1907.3-2050 could be a peculiar magnetic CV with the second longest ( 20.82 h ) binary period .
IGR J12123-5802 is variable in the X-rays on a timescale of \gtrsim 7.6 h. No coherent pulsations are detected , but its spectral characteristics suggest that it could be a magnetic CV of the Intermediate Polar ( IP ) type .
IGR J19552+0044 shows two X-ray periods , \sim 1.38 h and \sim 1.69 h and a X-ray spectrum characterized by a multi-temperature plasma with little absorption .
We derive a low accretion rate , consistent with a CV below the orbital period gap .
Its peculiar nIR/IR spectrum suggests a contribution from cyclotron emission .
It could either be a pre-polar or an IP with the lowest degree of asynchronism .